1. Are you sure you're getting 110/120V from your house? It's possible that either a breaker or, more likely, a GFCI has been tripped. Since it was working before you took you had your tires installed, I would suspect this rather than your adapter or anything in your MH. As you know, GCFI's can be finicky.
2. I don't have 50A service in my MH but my understanding is that the adapter should apply 110/120V to both legs. Here's a thread on a similar problem from the Forest River forums. The poster is plugging into a Honda generator, but that's immaterial, it has a standard 3-prong household-style outlet:
https://www.forestriverforums.com/forums/f23/50-to-20-amp-adapter-74179.html
Unfortunately, it doesn't look like it was resolved, but the responses should help you understand how it should work.
3. As with any electrical troubleshooting like this, you need to start at the initial supply point (your house outlet), determine if there's proper voltage there, if OK, move to the adapter, checking for proper voltage at the 50A end when plugged into your house socket, If OK, then to the input side of your breakers, etc. Randomly plugging things in isn't going to be diagnostic as to point of failure.
4. A multimeter is the best tool to figure this out. A non-contact voltage tester would work in most cases but it will only tell you if voltage is present, not how much. Both are good tools to have. An inexpensive multimeter like the $6.99 one from Harbor Freight would be adequate. Here are links to it, plus a non-contact tester:
https://www.harborfreight.com/elect...ters/7-function-digital-multimeter-59434.html
https://www.harborfreight.com/non-c...9.html?_br_psugg_q=non+contact+voltage+tester