I have this exact same issue with my WebEx Board 55. It just started within the last 2 weeks and I see that there was a Room OS updated as of January 16th, so I wonder if the two events are related.
The board home button works, and I can remote connect to the board and screen share or initiate a webex meeting and is shows up fine on the board. The main board screen, however, is entirely unresponsive.
Anyone have any ideas?