While cooking microwave went dead (all power gone).

I checked outside breaker, it was fine.
I then checked the 15 amp, 250V fuse in the cabinet behind control panel. It was blown. Used ohmmeter .
I also checked two door switches with ohmmeter. They were ok.
I replaced fuse and power was restored, but as soon as I tried to operate (cook) it went dead again.

What is the next likely step to check for problems.