furnace not lighting/co detector

Hi, we are having problems with the furnace on our new to us 2016 R182g.
Our first trip we turned it on to test it and it seemed to work fine, albeit with the ac fan blowing like mad. Thanks to the forum i learned how to turn that off.
2nd trip we ran it the 1st night and it seemed to work fine but it shut off at some point and did not come back on. The 2nd night it came on for a while but after it cycled off it did not come back on. The next morning it would come on for about 30 seconds and shut down. I suspect because it wasn't igniting.
that was 2 weeks ago. Today, I took off the face plate and outside screen and vacuumed it out. there was just a little dust and a few spider webs, not really dirty. Now the fan starts, then it clicks 5 times and shuts off. I tried with the stove lit to verify the gas was flowing, same result. I'd welcome any ideas!

I was about to post the above when my spouse noticed the CO detector was going off (several hours after the above). I pulled the fuse to silence it. Could this be related? The CO detector has never alarmed before, and I have windows open. Maybe it is just at its end of life?

The CO/LP detector is likely near the end of life. If I recall correctly, the red and green LED lights will blink alternating if that is the case and it will beep every few minutes. It does not have a fuse. It is hard-wired since it is a safety device. If it does have a fuse, then someone modified the wiring. 

If it is surface mount, I recommend replacing it with a flush mount model. It is more out of the way of foot traffic and looks better. It does cost a bit more though. This is the one I used:

Not to be a wise-acre, but have you checked your propane tank to see if it's empty?

Mine will click (spark) about 5 times and quit if it has no gas or there is air in the line. I can light and burn a stove eye for a few seconds to vent and air.

I definitely have propane. (Being a newbie I took the tank to get it topped off before our first outing, it turned out to be full!)   I have been running the stove as that worked to get the fridge to light (learned that trick on this forum). I've vacuumed and blown out all the webs and debris I could see without taking the unit out. I started to take off the outside plate to see if there's obstruction there, but it seems like it is getting good flow, it sends the sail switch, then shuts off. I also didn't want to have to reseal it unless I had to. I will see if I have time to try the troubleshooting info I found, but I have a service call scheduled as I'm needing it solved for an upcoming trip.