What causes a cordless AT&T CRL82212 base answering unit from not powering on?

The base station is defective, that is all that will cause this.

You set the cordless phone back into the charging base. After a few seconds (longer if in need of a charge), the cordless will register with the base establishing the connection required to place and receive calls.

When the base and handset stop talking to each other, it is generally because of a power interruption. Modern cordless phones transmit a security code from handset to base, when you start a call. This helps reduce the likelihood that you and your neighbor will be talking over each other, if your phones are on the same channel. If they get out of sync, usually the phone will just beep "out of range."

• To reset the chip which holds the security code:
  
  1. Place the phone back in the cradle for a slow five count. Then, pick it up and try it. If it works, you are done. If not, go to step 2.
  
  2. Unplug the telephone's base unit. Slide the battery cover off the handset, and remove the battery. Wait 30 seconds or so. Plug the base unit back in. Wait five seconds or so. Replace the battery in the handset. Place the handset in the base unit for a slow five count (as above). Now try it. This will almost always solve the problem.
  
  If this does not work, it may mean that the chip which holds your security code is now defunct and needs to be serviced. *
  
  
• Clean the battery contacts in case the battery is not getting charged. Clean the charging contacts on your base unit with a pencil eraser. This gives just enough abrasion to rub off any oxidation, without impairing the chromed surface of the contacts.
  
  
• If the battery is new and you are still experiencing problems, the phone will need to be services. Contact your authorized Service Center. *

Does the Phone Power Up?
1. When you pick up your GE cordless phone and press a button, the phone should beep as a confirmation that a button has been pressed. If the telephone handset does not beep, or if it does not respond to any buttons, the battery may be in need of a recharge. Verify that the cordless phone base unit is plugged in to an electrical source, then place the handset into the charging cradle. If no lights illuminate on the phone, or if charging fails to correct the issue, clean the metal charging contacts on the cordless handset and place the phone back on the charger. If it still fails to respond or to charge, the unit may need to be serviced or replaced.
Does the Battery Hold a Charge?
2. If the cordless phone charges up and appears to be ready for use but dies after only short periods of use, the internal rechargeable batteries may need to be replaced. Replacement batteries are widely available at electronics and discount retail stores. Note your phone's exact model number, as this number will be necessary when purchasing a replacement battery.
Listen for a Dial Tone
3. If the GE cordless phone powers on, and beeps when you press keys, but no dial tone is heard, one of three problems is the likely culprit. The phone's batteries may have an insufficient charge to fully power the phone, a condition that can be corrected by simply placing the phone back in the charger. If the batteries are charged, but no dial tone is heard, it is also possible that another telephone in your home or office is "off hook" or in use; verify that all telephones, fax machines and modems are securely on the hook. If there is still no dial tone, your telephone service may have been disconnected or require service by your local telephone company.
Listen for Static
4. On some GE cordless phone models, particularly older models, static may be heard if the radio signal between the handset and base unit experiences interference. Common sources of interference include unshielded electronics, appliances, and radio transmitters, as well as high-tension power lines. If your phone offers an option to change channels, try several different channels to see if the static is eliminated. If static continues to exist, or if static can be heard on wired phones sharing the same line, your telephone line may require service.
Verify Your Handset is Registered
5. Some models of GE cordless phones may display a message on the display screen that the handset needs to be registered. If this message appears, move the handset close to the base unit and press the "Prog/Mute" button near the bottom of the handset. Next, press the "Pager" button on the base unit (your handset may instruct you to perform this step). Finally, press the "Prog/Mute" button on the handset one more time to complete the registration process. Your GE cordless phone should now work correctly.The GE Cordless Phone brand is designed to deliver the conveniences of cordless home service with quality sound and features. There are many models of the GE Cordless Phone. The most current models, including the DECT 6.0, have standard features such as call waiting, caller ID, visual ring indicator, phone number memory and digital answering systems .
   
6. Before you use your GE Cordless Phone, ensure that you have all the parts. Your cordless phone package should include the phone base, a handset battery pack, a battery compartment cover, the cordless handset, a wall mount bracket, and a telephone line cord and AC power adaptor. Once you have confirmed that you have all of your parts, insert the handset battery pack into the handset and replace the battery compartment cover. Insert your telephone line cord and the AC power adapter into the phone base. The phone base identifies the telephone line as TEL LINE and the adapter as AC. Plug the phone base into the electrical socket. Place the cordless handset into the base. Allow the phone to charge for at least 16 hours before its first use. Failure to fully charge the battery before its first use will result in poor battery performance.
7. Once you have fully charged your phone, you can proceed with setting up your phone's features. If your cordless phone includes an answering system, complete this setup process first. Turn on the answering system by pressing the on/off button. The message indicator light will display. The cordless phones are defaulted to English as the selected language. To change your language preference, press the "Skip" button for two seconds. The language will change to Spanish. Next, you will set up your voice time and day stamp. While the answering system is on, press the "Answer" button on your handset for two seconds. The phone will enter the answerer mode. Press the "8" key. This will take you to the time/day setup menu. Use the number keys to set the hour and minutes. Use the volume up and down arrows to set the AM/PM. Press "#" to save. The cordless handset will also require that you give it a name. Press the "Mute" button for two seconds until the handset reads "ENTER NAME." Enter the name of the handset by using the touchtone keypad. Press the "Mute" button to save. Enter the default area code by pressing "Mute" until the phone displays "AREA CODE." Enter your three-digit area code and press the "Mute" button to save.
8. GE Cordless Phones are designed to be simple and convenient to use. To place or answer a call, press the TALK button. You can pre-dial a number by dialing the number before pressing the TALK button. When you are ready to make the call, press TALK and the phone will dial automatically. To answer a call that is waiting on the other line, press the FLASH button. If you experience call interference or bad reception while on a call, press the CHANNEL button until your line clears
9. 
   

here are some tips from my manual for out of range problems
hope they help
• Only one handset can be used to make or answer a call anytime.
If another handset attempt to do so, the screen will display OTHER
HANDSET ON and then OR OUT OF RANGE. You might press PHONE
or SPEAKER again until no other handset is using the line. Use the call
transfer feature to transfer a call to another system handset
or use the speakerphone feature so multiple members of your
house can be on an active call at the same time.
• Move the cordless handset closer to the base. You might have moved
out of range.
• Ensure that the base is powered up.
• Place the cordless handset in base cradle for 1 minute to allow the
cordless handset and base to resynchronize channels.
• If the cordless handset is in its base and the charging light does not
come on, refer to the charge light is off in troubleshooting guide.
• Reset the base. Unplug the unit’s electrical power. Wait for 15 seconds
then plug it back in. Allow up to one minute for the cordless handset
and base to reset.
• Other electronic products can cause interference with your cordless
phone. Try installing your phone as far away from these types of elec
tronic devices as possible: wireless routers, radios, radio towers, page
towers, cell phones, intercoms, room monitors, televisions, personal
computers, kitchen appliances and cordless phones.

Reset Procedure for Cordless Phones
Question:
What is the general reset procedure for cordless phones?

Answer:
1. Disconnect Battery from handset(s)
2. Disconnect Phone Cord from wall jack
3. Disconnect Phone cord from base unit
4. Disconnect AC adapter from wall outlet
5. Allow to sit for 30 min
6. Reconnect Phone Cord to base
7. Reconnect Phone cord to wall jack
8. Reconnect AC Adapter to wall outlet
9. Reconnect Battery to hanset until you click or feel the plug snap into place
10. Re-Register Handset by placing on main base in most instances.
<KEYWORDS="RESET, call,? can?t tone, dial no flashing, unavailable, range, of out working, not up, messed>

Reset Procedure for Cordless Phones
Question:
What is the general reset procedure for cordless phones?

Answer:
1. Disconnect Battery from handset(s)
2. Disconnect Phone Cord from wall jack
3. Disconnect Phone cord from base unit
4. Disconnect AC adapter from wall outlet
5. Allow to sit for 30 min
6. Reconnect Phone Cord to base
7. Reconnect Phone cord to wall jack
8. Reconnect AC Adapter to wall outlet
9. Reconnect Battery to hanset until you click or feel the plug snap into place
10. Re-Register Handset by placing on main base in most instances

* CHECK YOUR AC OUTLET WITH NO LOOSE CONNECTIONS.(remove multi adapters mostly caused problems)
* FULLY RECHARGE THE BATTERIES.
* CLEAN DE BATTERY CONTACTS IN & OUTSIDE THE HANDSET & THE BASE UNIT.
* IS THE BATTERIES DON'T GET CHARGED FULLY IN OVER NIGHT.PLEASE REPLACE THOSE.
* REPLACE WITH ONLY RECOMMENDED RECHARGEABLE BATT"S.
* PLACE THE BASE UNIT AT CENTRALIZED AREA FOR THE MAXIMUM HANDSET RADIATION.
* KEEP THE BASE UNIT AT SAME FLOOR.

Registering Handsets to the Base
Whichever handset you choose to charge in the base is automatically
registered to the base. Any additional handsets must also be registered to
the base before you can use them.
Be sure both handsets are fully charged.
One at a time, place each handset in the base. The charge/in use LED on
the base begins to flash, indicating the base is registering the handset.
Wait for at least five seconds, then pick up the handset and press
[talk/flash]. If the display shows TALK, the handset is registered. If not,
place the handset in the base to try again.
Press [end] and continue with the next handset.
Note:
Once both handsets are registered, it doesn’t matter which
handset is placed in the base or the charger.
When you charge the handsets, Caller
ID summary screen and the name of
the handset appears.

This can be find from uniden website.
http://www.uniden.com/pdf/DXAI4588-2om.pdf

most cordless phones need some access to 120 volt power to recharge the internal NiCad batteries. It wouldn't be cost effective to have on hand a bunch of charged batteries that you'd replace on a daily basis. they got to be charged up eventually.