Wow, Itunes Connect never ceases to amaze me.
I was getting "There are one or more errors on page"
The only thing I could find was a little red exclamation point next to the "English (U.S.) Primary Language" in the VERY FIRST drop down.
This is a bug, nothing is wrong with the languages it has to do with you missing the right size of screenshots.
Click on the blue "View All Sizes in Media Manager" link and click all the little boxes on the right (ex. Use 5.5" Display) to reuse your images for every size. DON'T FORGET to click over to the " iMessage App" tab as well (this is what I overlooked)
Click save, and then submit again.
I hope Apple really takes an Itunes Connect redesign seriously. Possibly the most buggy product they have made to date.