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Christopher (Drashna) in Beta 844-The background service failed to start
I am borrowing this from the Beta 822 thread since it worked for me:
Try resetting the settings.
I did not reboot, but just restarted the DrivePool service after deleting the directories mentioned, and that fixed it.
If you want to provide StableBit with diagnostic information before resetting the settings, run the StableBit Troubleshooter first: