If you want to troubleshoot yourself you can unplug the microwave from the outlet and test that outlet. Check for a correct ground and neutral as well as hot. There should be between 110VAC and 130VAC present. You should as a reference check the voltage at the outlet you plug the coach into from hot (line) to neutral. If you have 120VAC at the plug and a significantly lower voltage at the outlet in the RV you have a bad connection somewhere in between. If you are not comfortable working with normal AC line voltage do not do what I have suggested above. You need to have a qualified RV electrician look at it. Keep in mind that RV AC electrical systems are built to different codes (RVIA rather than NEC) so a household electrician may not be familiar with the requirements for a RV.