DIAGNOSIS The control panel is locked or the internal clock/control board has a power glitch. The '88:88' display is a default state, not a specific error code.
FIX First, unplug the microwave from the wall outlet for a full 60 seconds. Plug it back in. The display should clear. If it shows a time, press the 'Clock' button to set the correct time. The unit should now operate normally.
IF THAT DIDN'T WORK A hard reset may be required. Hold the 'Off/Clear' button for 5-7 seconds. If the display remains '88:88', the main control board may have a fault requiring service.
HEADS UP Do not try to reset the unit by pressing random button combinations. This can sometimes activate a demo mode, complicating the issue.