I can't upload screenshots to the new iTunes Connect Media Manager

As for August 8th 2016 Apple has changed it's requirement about Screenshoots. Now only one set of screenshots per device family is required.

This should simplify the process, however, the "choose file" option is disabled:

As you can see the app status is "Prepare for submission" and there is a build ready.

I tried using Google Chrome and Safari. It doesn't appear to be browser related.

Solution

I've solved this by changing main language of iTunes record. Please find the below steps.

Copy your app description and keywords to notepad.
Go to app information
In the right side clic on language and select the language you specified in XCode as main language(Localization Native development Region).
Delete unwanted language configurations from the same input.
Go to your build and add description, keywords. Choose file for screenshots 5.5 should be available now.