I received an email with the following message from Apple:
ITMS-90725: SDK Version Issue - This app was built with the iOS 15.5 SDK. All iOS apps submitted to the App Store must be built with the iOS 15 SDK or later, included in Xcode 13 or later.
Well, what's the problem Apple? I used 15.5. That's later than 15!
https://developer.apple.com/forums/thread/726841?answerId=748292022#748292022 answered here- it was meant to say iOS 16 SKD
Thank you for letting us know about this. We’ve corrected an issue so that the appropriate messaging appears in this scenario moving forward:
Starting April 2023, all iOS apps submitted to the App Store must be built with the iOS 16.1 SDK or later, included in Xcode 14.1 or later.
We encourage you to contact support if you have any questions about this or are seeing any further issues from your side.