Default cordova icon appears in App Store

I maintain an old phonegap project, that is now built with Ionic (which uses Cordova). For now, everything seems to work, but there is one problem: The iOS App Store icon does not show up, I see the default cordova icon instead.

Since providing the App Store icon with App Store Connect is not working anymore I did add a 1024x1024 icon to the app resources and the following line to the config.xml:

<icon height="1024" src="resources/iOS/icons/icon-1024.png" width="1024" /> 

But that did not help. I still see the wrong icon when I upload to the App Store. Everything else works fine, after the installation you can see the right icon on your homescreen.

Any ideas?