truma heater control issue

[TSF]

I tried to reset my Truma CP Plus on my 2019 Beyond 22D RV. After reset, I get the time displayed, and can get the clock and tool icon, but nothing else (no menue or status displayed). In Tool/Index, C3.00.01 is displayed. Can get no choices in Reset or Pr Set. Heater breaker and fuse are good. Running on shore power.
Before I tried Reset, it seemed to be functioning, but I couldn't get the heater to come on. Help!

[@Michael]

My guess is that the control panel lost connection to the Combi.

I'd call Truma. They've been very helpful with troubleshooting any issue I've had with mine.