How do i get my Ipod 6th generation to show up on itunes, then restore without telling me its corrupt!

Hi, so the story is about a month ago i had brought in my Ipod 6th generation in to an apple store because the sleep button was stuck down (that ipod was from this past christmas). It was under warenty so I got another one free, but now this new one wont

1. Show up on Itunes

2. When it rarely does (it shows up randomly even when its not plugged in) It says its corrupted. I hit restore and that bar goes on forever!

Ive uninstalled and reinstalled itunes tons of times and that doesnt work, ive restarted my computer which doesnt help. ive reseted my ipod by the buttons and the settings hundreds of times! Disk mode ive gone into but i dont really know whats supposed to happen after i plug it in. I have added songs to my library after my old ipod broke and before i got the new one if that makes a difference. My old ipod (6 generation) worked fine on my labtop with no troubles at all so im ripping my hair out trying to figure out what i need to do.