Unable to register handsets to uniden tru8888 base, I've deregistered the handsets and they show" place handset on main base to register" can't get any further

This could be several things.... the simplest is that a weak
handset battery can interfere with registration. Or,
does the handset display say "Connecting..." or
"Searching...." or "Out of Range / no power at base ..." ??

In these cases the handset is registered to another base and
must be de-registered before it can be registered again.

To deregister the handset:

Press and hold the [END] and [ # ] keys at the same time,
after a few seconds the display will say:

"System Reset, Deregister Handset"
press [SELECT]

scroll to "Base Unavailable"
press [SELECT] (chirps) press [END]

display reads "Place in base..." and it should be ready to
register.

Good luck!

To Reset The Main Base of a TRU8888:

Hard Reset: With Power off, Press and Hold Delete and Volume Up on main base and plug power back in (holding the buttons until you hear the successful beep)

Soft Reset: With Power off, Press and Hold Do Not Disturb and Volume Up on main base and plug power back in (holding buttons until you hear the successful beep)

First, select Deregister HS from the main menu. Secondly, press the red phone button and the # key simultaneously for about 5 seconds to finish deregistration. You will then see a message telling you to place the phone in the cradle of the base unit to register it to your unit. An "operation complete" message will confirm that the handset is now registered and ready to use. Good luck.

1-Press the hangup key (represented by a red phone) and the "#" key at the same time for at least five seconds.
2-Select "Deregister hs." Choose the handset and press the "Select" key (which also shows an envelope for messages).
3- Choose "Yes" to confirm deregistration. The phone clears its registration information from the base and deletes the link from its memory. The message "Handset not registered -- place handset on base to register. See owner's manual for help" now shows on the display. If you are out of range of the base, "Out of range" shows.
4-Place the handset in the base charging cradle. The phone automatically selects a new security code from those stored in the base.
5-Make sure your phone is working again after "Registration Complete" shows on the display
Hope this will Help. Thank you for using Fixya !!!

If the handset has previously worked with the base - press the hangup button and the # key at the same time on the handset for five seconds and follow the prompts to deregister the handset. (System reset - deregister HS - which handset) It will tell you that the handset is deregistered. Then put the handset onto the base and it will register the handset.

One has to completely deregister all handset by pressing end and # keys together till complete de registration is shown on handset screen. if the de registration is not done as above stated method the hand set will not register will show connecting on hand set screen.

place on base the will register your handset but make sure battery is charged now to deregister hold # end call button together for 8 seconds follow instructions for deregistering then once done place on handset to register

YOU might need to deregister the hand set first by holding down the red end (hang up key) and keep it down while holding the # key. If deregister wont work use base unavailable and yes, you are sure twice.

List the handset numbers of those working handsets
Using a WORKING handset follow these directions
Resetting Handsets
If you want to register the handset to a different base or
replace a handset with another one, you must first clear the
registration information from the base and the handset.
1. Press and hold [ ] and [#] for
at least 5 seconds, until the
SYSTEM RESET menu
appears.
2. Select the DEREGISTER HS
submenu. WHICH HANDSET?
appears in the display.
3. Move the cursor to select the handset ID to be de-registered
from the list, and then press the OK soft key. DEREGISTER HS
appears. CHOSE A NUMBER THAT IS NOT ONE OF YOUR WORKING HANDSETS
4. Move the cursor to select YES, and then press the OK soft key.
When ARE YOU SURE? appears, select YES. You will hear a
confirmation tone.
PUT THE HANDSET IN THE BASE CHARGER AND IT SHOULD REGISTER

Hope This Helps - It worked for me

I had the same problem!

What you need to do is hold the "end" and "#" key for 5 sec, which will deregister the headset then all you would have to do is place it back in the base for it to registered again.

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