The issue is now resolved.

Hi all, The problem fixed itself after about 6 hours. We noticed other apps had the same issue, so it might've been a glitch with Apple's in-app purchase system during that time. Best, Juno

The German version.

I reached out to them on March 17, and on March 27, they requested a screenshot along with steps to reproduce the issue. I responded immediately. However, since then, there has been no response from Apple. The problem continues and is affecting our sales😔

I also submitted a Feedback Report back on March 25th, FB13697245.

We are seeing a recent production issue with StoreKit 2 where some users complete a non-consumable purchase, but the app never receives the entitlement. Two users also reported that promo codes for the same product do not unlock premium. One user reported that premium unlocked automatically after about two days.