DIAGNOSIS A total, sudden power loss like that points directly to the safety thermal fuse. It's a one-time fuse on the control board that blows if things get too hot inside the electronics housing, often from grease accumulation or a failed fan.
FIX You'll need to access the control board. Unplug the grill and let it cool. Remove the hopper assembly (a few screws). Locate the small, white ceramic fuse on the board. Test it with a multimeter for continuity—if it's blown (no continuity), it needs replacing. It's a standard 250V, 10A, 277-degree thermal fuse you can find online.
IF THAT DIDN'T WORK If the fuse is intact, the problem is further back. Check the main power cord where it enters the base for any obvious damage or melting. Also, check the internal wiring harness connections to the control board—a loose connector from vibration can cause a total blackout.
HEADS UP Replacing the fuse is a temporary fix if you don't address why it blew. Before reinstalling everything, thoroughly vacuum out any grease, dust, or pellet debris from inside the base and around the control board and fan. A clogged fan intake is a common cause of the overheating that blows the fuse.