I ran into the same problem with an unavailable Nest Min that was fixed by a restart (~9:09am BST) which implies that my nightly restart is not working. I’ve switched the cron job to run every hour (0 * * * *) just to confirm that it’s working correctly, but assuming every is working fine with the scheduled restart, this doesn’t seem to improve things.
Again, adding some way to restart roon from Roon Remote would solve this, and again this has been requested and discussed by users for almost a decade here.