CFBundleIconName error for watch app

I'm attempting to upload a new version of an app last updated a year or so ago. I am getting an email from apple stating that


"

ITMS-90713: Missing Info.plist value - A value for the Info.plist key 'CFBundleIconName' is missing in the bundle 'com.richardwilliamson.whybrapp.watchkitapp'. Apps built with iOS 11 or later SDK must supply app icons in an asset catalog and must also provide a value for this Info.plist key. For more information see http://help.apple.com/xcode/mac/current/#/dev10510b1f7."

"

Most references I can find to this state that it's to do with migrating to an asset catalogue, however I did that quite a while ago without issue. This seems to be something to do with the watch app, but I am struggling to see any way to fix it.


Any ideas much appreciated.