Metadata issues

Several months ago, maybe a year ago at this point, I rebuilt my home server to transition from Windows Server (2012 Essentials) to Windows 10 pro. In doing so, I saved the HDs with all of my media, but forgot that Plex server stores its “application data” (ie, media metadata) in a separate location. So it all got wiped with the rest of the OS drive.

In rebuilding my media libraries, I’ve found that lots of metadata for my media either hasn’t been found, or is incorrectly populated. What’s particularly bad is that almost none of the album cover art (for my music) or DVD artwork (for my movies) has been found or downloaded - see screenshots below. Did I configure something wrong, or are the services Plex connects to for this type of artwork having issues of some kind…?

Some guidance would be helpful.