have you tried exchanging for a different MacBook Pro? or ask apple at the apple store if it's the laptop thats the issue or its iTunes? When I first got my iMac, last week, I originally got the 1,099 iMac without 4k, but it was too sluggish, so I ramped it up for 270$ more for the 4k, first there was an issue for me with iMessages and FaceTime, I was on the phone with apple for like 3 times on Friday last week, spoke to them literally 1-2 hours each phone call, I was transferred back nd forth apple rep was controlling my screen seeing what the issue was, then I pointed out the iTunes movie not playing, they couldn't figure out for life of themselves, lol, so was like "we'll have to contact you again with our senior advisor, is there a best number we can reach you at?" I was like ya sure, so it was scheduled Saturday at 5pm, but for some ODD reason, by 2pm yesterday it fixed itself out. Idk how, or why. But prior to that moment, I reinstalled my OSX, wiped everything out cleaned, tried apples method of reset pram, sign in and out of iTunes, redownload my movies and music, like 4x. It was ridiculous then I was like screw it I'll just wait for the update on Monday and maybe it'll fix itself, then magically like I mentioned, it worked out. So Idk, man. LOL. I hope yours did what I did, but I did everything I could. I was so close to just returning the iMac tho, I was like this is some B.S to deal with, I'll just use my old MacBook Air even if its sluggish lol.
Sometimes, it is just cos you got a bad apple and it just so happens, it keeps happening.