Actions always treat the currently selected files. If you want to apply the action to more than one file, select them all and apply the action then.
If you claim
is correct, then all mp3 files with an exactly matching named jpg file will get a cover.
Mp3tag takes the filename literally. It does not guess.
The message that a picture could not be accessed hints that there is no such file. Have a look at the picture folder and check where the differences in naming are.
I check and made sure all the files have exactly the same name.
But it still gives me the message that the image cannot be accessed
here are the mp3 file and the Jpeg file
doe to the file limitation I can only upload one file of each, it will be great if you take the time and make two folders on your desktop, duplicate the files and see if the action work, if so, then I can get the same workaround and solve the issue.
Would you please give them a try and see if you can make it work?