Not too long ago our power went out and a portion of our electricity would not return. I reset all the circuit breakers and everything looked ok on the panel, but no electricity.
I called my contractor that i've used for rennovations and various home repairs. He had me call his electrical sub-contractor, who told me that the circuit breakers that connect the sub-pannel often fail to restart without repeatedly resetting the master panel circuit multiple times.
You know what - he was right!
I reset the circuit breakers that connect the master to the sub-panel several times and everything went back on!