2008 discovery 40x. At some campgrounds when on shore power, our whole electrical system shuts down, (no power). Go on generator and power comes back. We "re-set" the inverter and go back on shore ...
As myredracer suggested, it could be a low voltage problem on the park's pedestal. Your coach probably has a voltage transfer box that ignores voltage if it is too low. (My 1993 coach has that feature and I would assume yours would as well.)
There is no cheap, simple solution other than using a portable battery charger. (I've done that to keep my batteries up while I used the house battery bank as in dry camping.)