Hi Chris,
this sounds like the "keyboard cable" isn't connected right. The ZIF connector and the latch are known for some trouble.
If you search this forum you can find some reports of PRS-505 owners reporting some or all key not responding after changing the battery.
First I would try to reseat the keyboard-connector.
If this doesn't work, you can try to reassign the working volume-keys to prev and next and holding them to menu and mark. (This will include installation of a CFW and cheating with applicationStart.xml)
HTH
Mark
|