Music not transferring to the samsung gravity? Is there something different with samsung that needs to be done?

I have copy and pasted music from my computer to all my other phones. For some reason it won't work on samsung blast or gravity. Is there a different step that needs to be taken? Was on the phone with tmobile rep for 3 hours and she could not figure out why it was not putting the music on my phones. She thought maybe something need to be imported? But didn't know how. Please help!!|||Try updating drivers, firmware and look for a sync software