Put the phone in the base station (not the charging cradle, the base that has buttons) for at least 20 seconds, so that it can resyncronize.
Rosehello's solution worked with one additional step for my handsets...After re-programming all of the 4 handsets, I had to unplug the base unit one more time and then it reset. Until that time it would only show"AL" and would not function.
You need to simultaneously hold down the red hangup and # buttons for about five seconds or until the handset says de-registered. You can then put the handset into the base unit and it will registere.
I had this problem myself on two Uniden TCX905 phones and that was the solution. I couldn't find it in the manual but verified it with Uniden support.
SOURCE: GE 25942 dial tone problems
After waiting for over 24 hrs for an answer from FixYa and then they wanted $10.00 and trying to fix it myself, I gave up. Threw all that c$$p into a box, took it back to the store and got my money back. It just wasn't worth the time and aggravation.
Usually answered in minutes!