Microwave displays H0 or HO and will not start; sometimes associated with child lock or demo mode.

Note: H0/HO on many Black+Decker microwaves indicates a special mode, not a failure.

• Disable child lock:
  • Press and hold the STOP/CANCEL button for 3–5 seconds until the display clears, or follow the lock/unlock instructions in your model's manual.
• Exit demo mode:
  • Consult the user manual; often, demo mode is toggled by pressing a sequence such as 0 multiple times, or holding a specific key combination.
• Power reset: If unsure, unplug the microwave for 5 minutes, plug back in, set the clock, and test basic heating.

If H0 remains and normal operation is not possible, refer to the specific Black+Decker model manual or contact support for the correct key sequence.