Use/Store Isolation Unit
I had the same issue on my 2017 26B Fourwinds. After doing the same troubleshooting you did I found a small in line fuse block/breaker ( I don't recall the proper name) about 1 in square with a tiny reset button. After pressing the button viola, it all came back to life. Mine was located under the dinette seat on the side wall. My charger is also locates in the same compartment. They're inexpensive and I keep a couple in the MH just in case.
This may or may not be your issue.
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