I think I have the same issue, but thought it was related to the new 'Base price' functionality, which I had enabled for my In App products yesterday. Unfortunately I did not test if everything was fine in Sandbox before I enabled the new Base prices ... Anyway, I am using RevenueCat and RevenueCat now no longer delivers those products to my app, it says in debug mode that all In App product IDs are wrong, so I believe this is the same issue.
Can someone from Apple comment or confirm, please?
It looks like only the Sandbox is affected, as all products are still delivered in Production.