Issues with album art in iTunes for Windows

iTunes for Windows 12.12.6.1 (latest) seems unable/unwilling to add album art to my .mp3 files.

I'm taking some time and "re-doing" my music library and updating several lower-bitrate files. The tags on these files are all accurate, and the album art is written to the tag as well as stored in the same folder as the .mp3 file.

Despite these steps I've taken, there are a great many files with no album art. I can go into the file info, go to the artwork tab, click add artwork, browse to the file, click open, click ok...but nothing changes. Still no album art. In many cases, iTunes cannot find album art either, though these are not obscure tracks, but I suspect this is a separate issue. I cannot imagine why I am not able to add a locally stored image as album art to a locally stored .mp3.

The files all "belong" to me from an OS (fully updated Windows 10 fwiw) level permissions perspective.

Anything I'm missing/anything I can try?