I have been using MP3TAG for quite some time and I have never had any issues with it. I have been trying to add music using Google Play Music app and use both Google Music Manager and the Play Music app for Chrome to upload my mp3 files.
For reasons beyond my understanding, after uploading the files to Google Play Music, the Album information is missing and replaced with a % sign.
They are fine inside MP3TAG editor, but have no idea what to try next.
As this is obviously a problem of the Google application, please turn to them and ask.
Everything else is just guesswork: is the size of the picture too large? Have you got the wrong tag version? Is the filetype compatible? Are the files OK (checks with mp3val, mp3diags, foobar2000 do not report anything suspicious)? Is Google the correct application for your purposes (which I doubt)?
Ok. I did some checking. I ripped a file with EAC and sent it to Google Play, the ALBUM info came in no problem.
I then added the ALBUM ARTIST info using MP3Tag and then sent it to Google Play Music. The ALBUM ARTIST info came in, but the ALBUM info was back to the % sign. It's not just Google Play Music. MP3 Tag is writing something or changing something that was fine with EAC and LAME MP3. Not sure how to proceed.
And, like I said earlier. I have used MP3Tag for more than 5 years and have uploaded music to Google Play Music for the last 3 years without issue.
I am using LAME 64 bit, with EAC. I will look into your recommendations of mp3val, etc...
One of the favourite hickups: do you have APE tags in the files?
You can see that in the column "Tags" if you have it or load the files and apply the filter
%_tag% HAS APE.
Remove these tag versions to get pure id3 tags.