Did the Duplicati service start at last boot of those systems? If not, does System event log show errors? For my system, Service Control Manager shows timeouts at start at boot, though a later manual start works. My workaround was changing startup type to Automatic (Delayed Start), after the ServicesPipeTimeout to raise timeout from 30 to 120 seconds was not reliable enough. I just tested booting with Automatic plus Recovery settings at infinite Restart. One timeout and no service. Maybe a service must start before Recovery helps?
By the way, it looks like Duplicati.WindowsService (if it actually starts) watches and restarts Duplicati.Server, however it’s not clear to me whether your service started and then stopped (somehow) or never got started.
(Above helped, but not enough.)
(Above worked. I added analysis. If you like, look over your server Duplicati.WindowsService.exe start times.)
Custom service properties can get lost, so I hope a better fix happens someday. Thank you for the software!