Is volume(sda2) your boot disk? Default permissions for accessing the root of your disk have changed. See
https://support.apple.com/en-us/101400
Try copying your entire Calibre library folder to inside your Documents folder.
e.g.
/Volumes/volume(sda2)/Users/<username>/Documents
and open it from there.
You could also try this in a terminal window:
ls -la /Volumes/volume(sda2)/Calibre*
to check file permissions.