Our WH switch has an error light (very small/faint) that indicates a high temp condition and all heat sources are shut down, sounds similar to your description. I’ve had this happen a couple of times in 5 years, cycling the breaker (110V) and battery (12V) at the same time will clear the issue. In your case the over temp thermocouple may have tripped or failed or the control board may have failed. If it’s just tripped my Solution May help.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks