Microwave Oven runs but doesn't heat - Amana...

Question

All,
Have a 1996 Over the range Amana microware oven that runs but doesn't heat. There appears to be nothing wrong with any of the touch panel controls, the fan starts and internal light goes on when the unit is started. Any advice would be appreciated in troubleshooting the problem and cost value of fixing this problem with the age of the unit. Is this the start of bigger problems? Thank you for your time in replying to this request for assistance.

Regards,
JB