What could be wrong if the heat pump does not blow much cool air inside and the lines frost up outside?

If the heat pump is not blowing much cool air and the outdoor lines are frosting up, it may indicate a refrigerant issue, such as low refrigerant levels or a refrigerant leak, which can impair the system's ability to absorb heat. Additionally, it could be caused by a dirty air filter or coils, restricting airflow and leading to frost buildup. Another potential issue could be a malfunctioning expansion valve or compressor, affecting the heat exchange process. It's advisable to have a qualified technician inspect the system to diagnose and resolve the problem.