Microwave part not working but Conection part is working.

I have a Kenmore Microwave/Convection Oven Model no. 721.67903601

First the unit started coming on when I opened the door. It didn't do it all the time but it got more and more frequent.

Now the Microwave part will not work at all. The Convection part comes on but the Microwave does nothing. The display panel lights up.

Thank you,

Annie