For me it was the Roon shortcut on the desktop. There was an incorrect or not updated specification of the directory: C:\Users\Uwe\AppData\Local\Roon\Application\200001272
The last digit or version number was incorrect or not updated.
Thanks for taking the time to write in! Sorry to hear you’re having issues getting Roon to function properly.
Most likely, your issue is due to build mismatches. I see from your account your mobile device is running Roon 2.0, while your core is currently running Roon 1.8 legacy. You can learn more about this here:
That link also includes a link to the 1.8 mobile download which should help you out.