[Andrew]

Well, a reboot should do it, but since your machine crashed that would have (rather forcefully) shut down the server. You might try turning off syncing, rebooting again just in case, and then trying to turn back on syncing. If that doesn't work then I think most likely there's something else that is the problem - a corrupted configuration file or something, in which case I would suggest contacting our support team via the Send Feedback item in the Help menu.