I bought an Optiplex 3080 SFF and bought upgrade parts for it but now it isn't running and I don't have enough troubleshooting skills to tell if the MOBO is dead or if the power button is dead. 😅

I can potentially shoot the ebay seller message to beg for product support.

I had it running with upgrade parts in for about 10 seconds and I held the power button to force it off. I assume I had it running once or twice before then, with the original configuration, too. It ran immediately after the "releasing extra power" trick where you unplug it and take out the CMOS battery and then hold the power button for ~15 seconds. Then put it back the way it was and close the case.

• Using non-original power cord
• PSU seems to pass BIST (no button, the light turns green for a few seconds and turns off when the power cord is plugged in)
• Have original parts and upgrade parts, can take out or swap out RAM, storage.

CMOS battery replacement? I have never done motherboard troubleshooting.

UPDATE: Edit: Yes it was simply the CMOS Battery. Popped a new 3V 2032 in there and the thing is running just fine with the original hardware.

Second Update: I contacted the eBay seller and they had notes for me about how to troubleshoot it that were identical to that of this community. The seller was insanely helpful, as were the comments I received here!