Missing 120 volts

We came home from our 2 week vacation and plugged our rv into the rv plug in our rv port. A few days later my wife told me that we did not have 120 volts. So I unplugged the cord and got my volt meter out and sure enough no volts.....so I went to where it is connected to the master switch and 120 volts there so some where under the concrete the power disappears. Something is amuck.....