You have a new version of your application in the Operator Cockpit and you cannot register it to test before upgrading. The button in the Versions screen is greyed out and not clickable.
Solution
Before you can upgrade an application with a new version, you have to register and test it. If the button is greyed out like this screenshot:
Remember that not only does the application need to be registered, but all the dependencies as well. Check the Registration menu to see which dependencies have and have not:
Notes