What does the UaDebug.log file say? If the service can't start it's almost always an account or permissions issue. Assuming that this was working without issue previously, I would verify that your service account wasn't disabled/removed and that you have a known good password. If the account checks out, then double check permissions.
You can of course try simply uninstalling and re-installing, but I'd recommend looking into the above log file first and seeing what the app is reporting.
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