Diagnosis
Localized failure of the membrane touchpad. Spills or repeated pressure on certain keys degrade the contacts.
How to Fix It
Clean the control panel with a damp cloth and mild detergent. Dry thoroughly. Press each non-responsive button firmly 10-15 times to try and re-establish contact. Power cycle the microwave by unplugging it for 5 minutes.
If That Didn't Work
The touchpad is a single, sealed unit. Individual button failures require replacing the entire membrane switch assembly. This part is mounted behind the front control panel trim.
Heads Up
Avoid using abrasive cleaners or excessive moisture on the touchpad. Spills that seep into the edges of the panel are a common cause of this failure.