I have my SMT1500C connected to my computer via USB and it only retains the USB connection for 15-20 minutes after login before disconnecting; the only way to get the connection back is to unplug and plug in the USB cable again. When the connection is lost, Device Manager shows the USB connection is working under Human Interface Devices and shows the unit under Batteries. Also, the APC PBE Agent service is running and restarting the services doesn't resolve the problem. I've had this unit for less than a week and this has been an issue from day 1. 

System Info:

Windows 10 Pro x64 v20H2

PowerChute Business Edition 10.0.1

Smart UPS SMT1500C