Can't submit IAP for review

Looking for some advice to get past a road block submitting a macOS app for review with an In-App Purchase.

The IAP is a non-consumable one time purchase that will unlock additional features.

I've submitted a new version of the app but when I try to attache the IAP I get a warning:

Unable to Submit for Review Your first non-consumable in-app purchase must be submitted with a new app version.

Anyone able to shed some light? This is my first attempt at attaching an IAP and I'm stumped.

Thanks, in advance.

Can't submit IAP for review
 
 
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