Strange 500 starting problem

I have a strange starting problem I have not been able to find when searching. The machine is a 2007 Sportsman 500 Deluxe EFI.

ATV ran fine, was parked in the garage. The next day, it would not start. When you turn the key to run, the dash goes through it’s dance. It normally won’t turn over, and the dash seems to clear to just a check engine and HOT graphics. Then it reboots and starts over. If you hold the key on start, then it might crank during one of the reboots, almost catch, and then stop again.

Using the pull start didn’t work either.

Any ideas? It sounds like some kind of fishy electrical problem I am really not looking forward to. Didn’t expect my first post would be for a problem.