thanks for the feedback. I have a bit more info to also pass on - we're fortunate that we are able to contact the previous owner who is very helpful with any tech info we might need (tho not always able to respond quickly, hence my post here), and after hearing about our issues he said he's also had similar issues and suggested removing/cleaning the sail switch. I removed the sail switch hoping to find a bunch of hair or moths or caked up with dust, but no - it looked pretty 'clean', so I didn't expect much to be resolved after screwing it back in. But during the whole next day the system seemed to perform 'normally'.
I did not expect cleaning the sail switch to cure anything. I don't know exactly what it does but the R&R seemed to do the trick; before the system simply would not 'activate' - no clicks, no fan blowing without heat, no igniter clicking - just 'nothing' - there was simply no 'feedback' from the DOMETIC thermostat. There were also no LED indications from the circuit board indicating an error - that part really surprised me - I expected there to be 'some' kind of error indicating the problem but nooooo...
So, we're going to continue to 'deploy' the camper in our back yard for the next several weekends and see how it goes, and we'll get another sail switch to put in the spare hardware drawer...
The camper is still under warranty so yayee for that - we just did not expect to need it for a while, but, here we are and away we go