Why won't my GS3 music player recognize the .mp3 files I just added?

A

AC Question

Months ago I added some music to the 64 gig Samsung sd card on my phone and have enjoyed the playback. I recently added some more music, mp3 again to be specific, to the sd card in my Galaxy S III. I did so from my home PC just as I had done before. The newly added mp3 are not playing on the phone and I get the message "Sorry, the player does not support this type of audio file". I am not sure why when it plays other mp3s I have on there. It's the stock music player that came with the phone, the same one I have always used. Any thoughts?