I had the same issue. To solve it, the unique thing I had to do was "Clear History and Website Data..." within Safari (version 8.0.3 in my case).
Please, keep in mind that I speak from my experience and that worked for me. I cannot guarantee this as a general rule to fix the problem. Nevertheless I can assure that I tried several alternatives explained here and the one I just described was the solution for me.
It seems to happen if you are too quick between the build finishing "processing" and it being attached to a version and the version being submitted. I just published two apps in quick succession and the second submission had this problem while the first was fine. The only difference - speed of clicking the submit button.
Logging out and back in made no difference - the "problem" is with the submission.
I removed the just uploaded build from the version and then re-attached it, proceeding as normal to submit the release to Apple with exactly the same build and submission artifacts as before, except this one "saved" and went into the review queue.
I got this problem in Chrome browser. Switching to Safari worked like a charm for me.
I had the same problem. just sign out and sign in again. it should work.
I'm stuck on this too; and have had to work around several other iTunes Connect bugs just to get to this point. What were Apple thinking by releasing this iTunes Connect version? It's completely ridden with bugs!
Sorry, I've tried everything I can: Filing a support case with Apple appears to be the only 'solution' at this point.
Make sure the Version you have on iTunes Connect and the version you gave in the Info settings in xCode are exactly the same. I had 1.0.0 in iTunes Connect and 1.0 in xCode and it kept giving me this error message. I changed it to 1.0.0 in xCode and it worked perfectly.