The F7 error code indicates a problem with the 1100W Inverter. You can sometimes resolve this problem by unplugging the microwave for 1 minute. Plug it back in and see if it operates properly. If the error code returns, the microwave will need to be serviced by a technician. Microwaves are inherently dangerous to service. Internal capacitors can retain a lethal electrical charge even when the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal repair. These are the reasons why we recommend having a service technician diagnose and repair this microwave failure.