Apple has released new version of iTunes Connect & I got an error message when I tried to set Screenshots on itunes connect for my app.
\"Images can\'t c
Extending Roman B. answer. This is still a problem, I was uploading a cordova app. my solution using mogrify:
mogrify
brew install imagemagick * navigate to `platforms/ios//Images.xcassets/AppIcon.appiconset`* mogrify -alpha off *.png
Then archived and validated successfully.