I replaced my old NAS but kept the drives to migrate the data. All done and the files are working as they should like before.
Now my plex server shows all the movies like before but can´t seem to find them on the server even if the library is in the same place and seem to be working outside of plex.
I thought I ask if this is a common problem with an easy fix or if I should reinstall the plex server and start over.
If the files are there but the server has them marked as “Unavailable”, this is expected.
The new DSM installation doesn’t always carry forward the permissions from your previous configuration (the backup config / restore config steps you take).
If this is all making sense, go to Control Panel - Shared Folders and EDIT each media share’s Permissions tab giving user ‘Plex’ the appropriate Read or Read/Write permissions.