From the IAP FAQ:
App Review has recently approved my application, but my In-App Purchase identifiers in the production version of the application are being returned in the invalidProductIdentifiers array.
When an application is approved, the developer must also approve the application for release to the App Store. On approval, the application ID is activated to the App Store. The same activation is required for the in-app purchase identifiers and can only take place once the application is activated. In some cases, the activation of the In-App Purchase identifiers may lag up to 48 hours following the activation of the application.
Using App Store Connect, I suggest you confirm the status of the app and the IAP products, and your contracts to be sure none are pending agreement. Might want to also check via Member Center as well.
Still no joy, ping support via the contact us link below to ask them to take a look on their side.