Do you have the APC USB plugged into a USB3 port? I don't know if/why that could be a problem.  Maybe for some reason the USB 3 port is dropping the 'connection'.  If so, use a USB2 port, and repeat.   This is totally irrelevant, but this is what happened to me when I went from USB UPS Type to ModBus (which dropped communication since I actually have CyberPower), and back again.   Aug 11 20:59:34 UNRAID apcupsd[1202]: apcupsd exiting, signal 15 Aug 11 20:59:34 UNRAID apcu