Bought a replacement battery for extra handset and used the adaptor from the base unit to try to charge the battery. This did not work. Charging notice did not appear in the display window and the charge indicator light does not light up when I place the handset on the charger. Do I have to replace the charger, the adaptor, or both? Do I have to buy a new phone ?

SOURCE: Uniden DCT648 register phone problem

I have contacted Uniden about solving this problem. They suggested I clear the eeprom on the handsets and reset the base. To clear the eeprom detach all of the batteries and reattach while holding the star and pound. You'll hear a beep. Press select and the unit will clear the eeprom. Now hit end and the unit will say "Welcome...something or other". Next unplug the base unit reattach while holding delete. Next hit delete twice...the base is reset. Apparently this is the last possible solution to marrying the handsets and base. This didn't work for me and the units have been declared dead. Good luck in solving your electronic problems.

SOURCE: Handset not registering with base

You could try to clear all the memory from the base unit and start again!!!
Instructions to clear phone (Uniden 8855).
1. Go to your base unit.
2. Put your flip phone in the cradle.
3. Press down and hold down (AT ALL TIMES) the end (find hs) button.
4. Whilst holding down this button, take the power plug out of the wall.
5. Whilst still holding down the end (find hs) button, plug the power back in.
6. When you hear a beep from the base unit system.
7. Let go of the end (find hs) button.
8. Your phone memory should be cleared now and you are ready to repeat the process of registering your base and additional handsets.

SOURCE: unable to register handsets to

From the manual:

1) Before registering the extra handset, the battery pack MUST be charged for 15-20
hours.
2) With the main base in standby mode, press the MENU soft key on the base.
3) Press /vol/∧ or /vol/∨ on the base to select H S R e g i s t r a t i o n, and then
press the OK soft key.
4) On the handset, press and hold # for two seconds. To cancel registration, press
the CANCEL soft key on the base.
5) While the handset is registering, H a n d s e t R e g i s t e r i n g will appear in the Handset
LCD. When R e g i s t r a t i o n C o m p l e t e is displayed, the handset has been registered
to the base. If R e g i s t r a t i o n F a i l e d appears, please try these steps again.


Geno

SOURCE: Panasonic KX-TGA101S base not charging.

Here are a couple things you can try.

Clean the charging contacts, this can be done two ways. The manufacture's recommend using a pencil eraser. I recomend using a q-tip and some rubbing alchol. Just rub the alchol soaked q-tip on all the metal contacts on the bases and the bottom of the handset.

Gooo luck.
Hope this helps

SOURCE: Panasonic KX-TGA101S base not charging.

PyroPC Man is right! Thanks!