How did you install Picard? Maybe using Snap?
If you use the Snap version you must be aware off that Snap provides a sandbox for applications which restricts the files and folders the application can access. By default Picard has only access to your home folder. You can additionally give it access to mounted external media, see http://picard-docs.musicbrainz.org/en/getting_started/download.html#installing-with-snap
Giving access to arbitrary file locations is not supported by Snap, so if your files are in different mount points this won’t work.
The alternative would be to use the Flatpak version of Picard. Flatpak has the nice ability that it allows users to grant applications explicit access to arbitrary filesystem locations. I don’t remember the details right now, but if Flatpak is an option on CentOS 7 I could help you with that.
A RPM version of current Picard on CentOS 7 probably is not feasible due to outdated dependencies.