I was called to a home to check on a system that was not cooling. Upon arrival, I found that the system was not cooling upstairs. I checked the unit and found that the wire at the condenser unit was not getting voltage. I checked the wire at the air handler unit and found that it was not getting voltage. I inspected the thermostat and found that the unit was set to conventional instead of heat pump. I adjusted the tsat and the system kicked on cool and no issue with the unit. I showed the homeowner how to work the tsat and explained the maintenance program that they wanted to sign up for. I also recommended replacing the filter as it was very impacted. The customer paid a $79 diagnostic fee with a credit card.