As this is nearly my 10th android smartphone and I have always used custom roms, I wanted to try the "original" Samsung ROM.
But I faced this issue : same mp3, when on sd card (in Music directory) are not recognized by the build in audio player.
So I decided to download and try some players from the playstore.
The only 2 ones that can see my mp3 are n7 (but refuse to play some formats like .ape with free version) and "audio player" (from Mobile_V5).
Same files, when are copied to internal Music directory are seen.
The SDXC card (Samsung 64 GB UHS-1) is recognized by the device, when I put files on it, I can see/add/move/delete from a file manager (mine is X-plore).
I've also tried several apps from the store that propose to rescan the SD card, and didn't help.
So, if you can tell me more about this problem please ?