When you say "checked at the plug" do you mean at the receptacle that the microwave actually plugs into?
Check the RV's breakers at the power center. There is probably a dedicated breaker for the microwave. It could be tripped.
Is the microwave plugged into its receptacle?
2011 Dodge Ram 1500 HEMI Quad Cab (new Chrysler rebuilt engine installed March, 2022)
2011 Jay Flight 26BH (FOR SALE - I bought a house and don't need it anymore)