2020 kenworth t680 APU unit trouble

I am encountering a problem with my electric APU unit. When the tractor engine is running, both the front AC and sleeper AC provide cold air, and everything operates as expected. However, when the engine is turned off and the APU is activated, the outside units turn on, but only warm air is produced in the sleeper. The front AC works perfectly when the tractor engine is on, and I have also checked the freon levels, which appear to be within the correct range. Could anyone offer some advice on the possible cause of this issue? This is a 2020 kenworth T680 model, and I would be very grateful for any suggestions. Thank you.