Did you try a spare battery? Everyone should have at least one spare in the rotation so you don’t need to charge a hot battery.
If you see no voltage at the battery suspect a bad bms. (Replace battery)
If you see low voltage at the battery suspect a bad charger.
If you see full voltage at the battery then the search is on for a blown fuse, bad key switch, a connector that came unplugged or a broken wire.
Good luck, keep us posted.