Furnace burner wont kick on..

[onespeed]

On our 2015 Solitude 320x, the burner won't light on the furnace. The blower starts up, but shuts off after a few minutes, I think because the burner not working. It's a Suburban SF-35Q. It was working fine last month when I checked it. LP tank is full (and the valve is open) and the 12V battery checks 13.5V strong. Kitchen stove and water heater both working fine. Researching tells me to check the sail switch first. I could do this if I could figure out just where it is. Looking at the unit with the access panel off, I don't see it. I'm guessing that it will have to be slid out a ways. Has anyone done this before?
I think after removing the gas line on top and some screws on the flange, it should slide out far enough to see something, without disconnecting the ductwork. I'm willing to try it, but if someone knows this procedure, I would appreciate any guidance. P.S. I don't know why these piks turned sideways on me. I don't know how rotate them......

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