Jellyfin library empty on Synology NAS

[Efficient_Good_5784]

Ok, so I think I understand what's going on now.

You most likely have a shared folder on volume1 named "Media". You now have a shared folder on volume2 named "Media".
This is what's giving you an error. The GUI that Synology made where you add shared folders doesn't display which folders reside in which volume, so it's a guessing game.

I would try renaming either of the shared folders so that both are not "Media". Go to the control panel and edit the name of one of these shared folders.
If you rename the "Media" folder in volume2, just select that new shared folder name in the container manager setup.