Still don't know if you have a 30 amp rig or a 50 amp rig. Having that kind of basic knowledge helps us help you. Consider putting some basic info in your signature. Like the Bounders age, length, whether it's a gas or diesel, and if it has slides.
If it's a 30 amp rig, we've been through a long period of hot weather. A 30 amp power head on the end of your shore power cord is the first thing I'd check. They do open circuit after overheating for weeks at a time. While inspecting that, I'd look at the 30 amp power socket. How's it look? Then I'd measure the voltage.
If that was good, then I'd head to the power compartment where the power cord enters the RV and if there's a junction box, open it up and check that the wire nuts are nice and tight and none of them are melted. Then plug everything in and measure the voltage right there.
If that's good, then I'm afraid you'll have to pull the transfer box and check in there for loose or open circuit wires, a bad relay (available at Amazon), broken terminals, or loose terminals because that's exactly where the power goes. The power wires from the genset meet up in there and ALSO attach to the transfer relay, just like the incoming shore power. When the genset runs, it actuates the transfer switch so it closes and routes the genset power to the RV. When you're on shore power, the transfer switch just sits there, but the contacts are closed to allow shore power to the rig's Circuit Breaker panel.
Guess what...every equipment test I've mentioned in this post I've had a problem with at least once in my '94 Bounder over the 12 years I owned it. And each was solved or found using my handy digital VOM.
Good luck. Hope you find a good mobile tech. Check in your area on RVServiceReviews.com for a good tech or shop.