AWOL albumart - a real pain

Hi all

A number of years ago all the albumart (in jpg forat) from my mp4's & mp3's (which are in their own folder and which I play in MonkeyMedia) vanished) and were replaced with the generic MM icon only. Using Icaros and mp3Tag they miraculously reappeared (all but 10); with some cursing & swearing I managed to make 2 reappear so far, my 3rd is a absolute pain in the butt, the artwork is visible in mp3Tag and MM but refuses to show on the physical mp3. In mp3tag I have removed the tags and repopulated them (& Albumart) - still without success (even after saving everything) - Windows itself refuses to cooperate - any suggestions?

And which is it? MP3 or MP4?

And perhaps to save a couple of Qs&As: try to follow these hints for support requests:

esp. the part about checking the files for errors, screenshots to illustrate the problem

I haven't looked over my mp4s for correctness, but my mp3's I'm focusing on at the moment. PS: sadly I was born with brain damage; so could all (or any) responses & suggestions be in plain English and non-technical jargon; thanks

please check the mp3s with the tools suggested in the linked thread and see if that helps.