I recently acuired a secondhand NUC8I5BEH and installed proxmox on it. But it randomly is unreachable from my LAN. There are no errors in syslog. When I connect a monitor there is no signal. So the NUC seems crashed. The fan is spinning and the LAN lights are on. It’s not viewable on my unifi controller and it’s not pingable. Where can I start looking for the problem?
Try following some of the advice in this thread. Hardware tests if the BIOS supports it. Maybe try underclocking or undervolting the CPU is BIOS supports that. If you can pull a RAM chip and test with just one, then test the chips individually in each slot, that’d be something worth trying. I’m shooting from the hip, but these are things that could help isolate a possible hardware issue.