Did you move to a new server or did you restore a backup?
Yes, restored a backup
Unfortunately, this means that you have to uninstall and reinstall ARC. (And you will lose all ARC downloads in the process).
Restoring a backup is currently being treated like a entirely new server, meaning that you have to to a complete first-time resync with the server. Roon Labs said that they are working on improving this, but at the moment this is what it is.
Wow.
I was able to go into Arc offline mode to access settings and disconnect from Roon Server. I’ve subsequently reconnected to Roon Server and Arc appears to be syncing for the first time. If that doesn’t work, I’ll follow your procedure.
It would be good if restoring from backup instructions included this caveat that Arc has to be disconnected FIRST and reconnected after Roon restores backup. Also, the "can’t connect message should include a link to Arc settings because going into off-line mode to do so was a fluke on my part.
Interesting, I don’t think someone has tried this before and I didn’t know. Another thing is that on Android you can alternatively just clear the cache (though on iOS there is no option for this).
However, I’m afraid that (as far as anyone knows 
) it will still be like a fresh install and the downloads will be gone. Though maybe you can get around changing all the settings again.
Any idea how long a new Arc sync takes? (It’s been 5 hours so far, and no indication when it will sync.)
Depends on the number of tracks in your library. It takes less than a minute or so for me with 50k tracks, but very large libraries can take a long time, I think (or possibly fail completely). If you experience unusual problems, open a case in Support.
I have 150k tracks listed and it just finished, so took about 5.5 hours to rescan.
Thanks for your assistance.
150k is not very far away from the recommended ARC maximum (though it varies by phone and perhaps library specifics). The duration sounds a bit excessive to me, though it’s possible that it grows according to some power law with the number of metadata crosslinks. Well, as long as it works - good luck
Arc has usually worked unless there was a network problem or an update to Roon. But it appears to be working as it has before. I try and keep Roon clean (so if there are cross links it’s not anything I knew I was doing), but will keep the 150k max in mind going forward.
thanks again.
All the credits and other links between items that are being automatically generated. The number of links between nodes grows faster than linearly with the number of nodes, as in any network. This is why the number of albums (and their credits) becomes a problem for Roon at some point as albums are added to the library. And on a phone, this database has to be maintained in a very constrained environment.
See here for instance:
When I turn off tailscale on my phone it’s difficult to connect back to it. Maybe I’m in a low signal area but not sure. Will try again when I’m outside.
@Abrahams_Bogere Are you sure you posted in the right thread? The OP here uses port forwarding (not Tailscale) and the cause of their issue was already found.
Oh no. Mine seems to be different cause. I haven’t done enough extensive testing to determine the issue. More than like maybe signal being low in certain areas.
This happens to me every few months, unpredictably. Sometimes restarting Roon Server cures it but not always. And I’m often not in a position to do that remotely. The nuclear solution that always seems to work is to delete ARC from the iPhone and reinstall it. Downloads disappear and it takes a few minutes to re-sync, which is annoying, but it’s a reliable, easy fix. The alternative is to use Qobuz player, which seems to be solid with a decent connection. But I prefer ARC, when it’s working. I write it off to some combination of my weak-ass, old phone (iPhone 13) and my largeish library (94k tracks). Life goes on.
