There are 4 places where you can move the LMA agent to the top.
Do you have it in the top position under
Settings - Server - Agents - Albums - last.fm ?
And if you did, was this before you added all those files into Plex or after?
Same applies to the ‘use meta tags’ checkbox. Did you activate it before or after adding the files?
If the answer to one or both of these questions is ‘after’, then you’ll need to perform the Plex Dance with the affected albums.
(With music you can omit step 4)