I have a 97 Beaver Patriot, it has the older aqua hot with a single switch in the kitchen for the diesel burner. So it may be the same model you have.
You might check and see if your's is the single pump model like mine, if it is, there is a gate valve (like a hose faucet) that turns on antifreeze going to the heaters, my RV guy turned it off and forgot to turn it back on and I had no heat until I opened the valve.
It could also be that it lost prime, I've not read to much into that other than seeing others post that it has a specific set of instructions in the service manual and it's not for the feint of heart.
If you get down in the basement you should see the antifreeze lines running to the front and back zones, reach up and touch them (gently as they can be 180+ degrees), you should feel heat. If you don't, then it's probably what I mentioned above, either the valve is off or the pump lost prime.
You should also check your anti-freeze levels, but that requires the aqua hot to be cooled off before opening the radiator cap. Do not rely on the overflow bottle to verify the internal tank isn't low.
If the antifreeze is low that could cause it not to be able to pump to the front and back zones, and can also destroy your aqua hot.
I'm planning on checking my levels before I head out this weekend. With winter fast approaching, probably not a bad idea for others to check their levels as well.
Tim & Ann