Buderus GB142 doesn't power on

We've got a Buderus GB142 that was installed in 2007 or so. It was chilly yesterday so I turned the heat on for the first time this season, and after 15 minutes, no heat. So I went down to the basement and see that there doesn't appear to be any power on the GB142's control panel, nor to the AM10 Outdoor reset.

I flipped the main power switch next to the boiler off and then on, no change. I checked the outlet that's in the same junction box (same power source) and there's power to the outlet. Yes, the main power switch on the control panel is On.

In the past, we had some issues with the outdoor reset shutting off, but this was due to a loose control wire from the GB142. Tightening that fixed the intermittent problem.

So, Questions:

- If the AM10 is dead, will that cause the GB142 to not power on at all? Nothing is lighting up on the GB142 control panel.
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- If there's power to the boiler from the main shutoff switch, what might cause it to not power on at all? Faulty control panel? An internal fuse or breaker somewhere?

I'm handy with electrical and electronic stuff so I have no problem swapping parts out, but I don't want to buy stuff I don't need. Any guidance on where to start troubleshooting this would be appreciated.

Thanks!