Details are missing if you really want help:

"Battery is at full power", what exactly does that mean? You referring to the internal battery or external battery? If internal, I assume you cracked open the radio and checked the voltage with a meter? If external, that won't matter in your case because the external battery does not directly power the radio.
Have you tried pressing the reset button hidden behind the grip insert if the internal battery is actually in good shape?

The times I have seen your same above issue, it turned out to be a dead internal battery. Worst case, you'll need a new main board.