When I arrived at home, I was told upstairs cooling wasn’t operating. I set thermostat to cooling mode and started diagnostic. I had error codes on furnace to replace air filter. Air filter was caked on with a lot of dirt and debris. After resetting system, and setting to cooling mode again. The system operated correctly and outdoor unit started cooling efficiently. I then went to check other unit to replace that filter. Tenant had an extra filter so just replacing one today. Turned off cooling mode and system is operational upon departure.