stuck on 'refreshing your media'.

There’s no general “clean” button on MP3Tag.  To clean via MP3Tag would mean to eliminate info. in tags that is not needed or to strip away long tags, and likewise to convert the tags (if needed) into the ISO type that the Clip will accept.  Many of these tasks can be done viaq batch tasks–that is, to all the files as a whole, rather than 1-by-1.