DIAGNOSIS H97 (or sometimes just H-97) is a communication error between the main control board and the touch panel/operation board. It means the microwave's brain isn't talking to its buttons and display properly.
FIX Unplug the microwave from the wall outlet for at least 5 minutes. This is a full capacitor-drain reset. After plugging it back in, the error may clear. If it does, set the clock and test it.
IF THAT DIDN'T WORK If H97 returns, the flat ribbon cable connecting the two boards might be loose, damaged, or corroded. Fixing this requires disassembling the unit to check the connections, which involves dealing with the high-voltage capacitor—a dangerous component even when unplugged.
HEADS UP This is a less common but known fault. If the hard reset doesn't fix it, it's generally a professional repair job due to the internal safety risks. Don't try to open it up unless you're trained to discharge microwave capacitors.