I had the same problem happen to me. I contacted Thor and they had me hold in the emergency start switch down for like 1-2 min then try to start...nothing. They told me that if the chassis battery was completely drained (not just low), the coach batteries would not start the engine. I'm not sure why this is the case. It seems that it would just use the coach battery but apparently that's not what its doing. It seems to being trying to "recharge" the chassis battery which doesn't work if the chassis battery has drained too low. I charged the chassis battery and everything was fine and it has not happened since. I guess the emergency start will only work in the case where the battery is borderline low.
From this I decided to get a charger/jumper that can be charged up and/or connected to shore power just in case it happens again. I have not had to use it yet and I'm keeping my fingers crossed that I never will
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