On arrival, the homeowner informed me that the upstairs system was failing to keep up with the thermostat setpoint throughout the day. He said this issue has never happened before in the past and the system has worked good previously. I turned the inverter system to max stage and performed a complete system checkout. I noticed my suction line pressure was well below design specs and my suction line temperature was running warm. I opened up the evaporator coil panel and found that the coil was beginning to frost over. I verified appropriate airflow of the system and verified there were no air flow restrictions of the system. After further diagnostics, I was able to pinpoint the cooling issue to an indoor metering device failure. The metering device is stuck closed and will not allow any refrigerant to pass through into the coil. I tested the metering device by adjusting the heat pump valve on the outdoor unit, which confirmed the issue. It is recommended that we replace the indoor