Payload bundle identifier mismatch with Xcode at validation step
I was having the exact same problem. After doing all the things you probably did, I finally restarted Xcode and that did the trick. Hope that worked for you too.
Rule #1 of Xcode: always try restarting Xcode first (like its 1999). But if that didnt fix this issue (didn't for us) - make sure you have actually created the new iOS App in iTunesConnect.