Apparently that skim coat made it just a hair to high and when the bars were reinstalled, just a hair too low.

.#8 Reinstall drywall.

We will have to remove all of the siding, demo out the old stuff, treat the wall cavity with microban and reinstall the hardiplank.  

However, he was supposed to return to complete the finishing work after I had laid floors and reinstalled the tub.

If you just get electricity turned on then they will take the gas meter and charge you to reinstall.  

If so, then we reinstall insulation, drywall, etc.Of course, curing the root of the problem has to be addressed first and foremost.

Well, I guess if the carpet is still in good condition, you could just pull it up gently, replace the pad, and reinstall the same carpet.

The other unit also has a gas range in the kitchen.This system is a retrofit of sorts because of the order of events during installation and the unknown expectations for the solar system (re installation date and performance). 

Please uninstall and reinstall and let me know if that fixes it.

Reinstall and recheck operation.If You can find the paperwork that came with the heater, You will be able to turn on the self diagnostics and read the LED codes.John