After fighting the seat switch and getting that fixed, now when I try to start the mower......it fires and takes right off but then dies immediately. I'm sure it's another stupid safety switch......Is anyone familiar with them and which one it might be?

Winter corrosion on the safety switch. Penetrating oil on it and after 5 minutes blow off with air pressure.
Follow the wires because sometimes the mice like to nip them in winter......they used vegetable oil in the wire harness manufacture to save a few cents...or maybe to get guys back in the shop for a 150$ new wire harness...what do you think ?

here's where I get my tractor info, from a huge group of experienced folks https://www.mytractorforum.com/

Double check it is electrical problem first. A bad/gunked up carburetor will do exactly the same thing. Feeding ether into the carb/air filter will tell you quickly if it is a fuel problem or not. Simple , quick test.

If electrical related , some mowers have interlock switches on the mower/deck engagement and the brake pedal.
And yes , some newer cars/mowers have wiring with soy based products in the covering . Mice like chewing on them.

Sounds to me like the electric fuel shut if it has one. Look on the bottom of the carb for wire. They are notorious for getting green ethanol goo stuck in them and not working. If it has one there should be a loud click from the carb when the key is turned on.