Hi,
If you don’t have any issues with your build, you should be absolutely sure that everything is OK in your account.
Look at this post: https://medium.com/wolox-driving-innovation/3b361da0f038
In general:
- you have to sign Apple’s Paid Applications Agreement.
- make sure you Enabled In App purchase in App ID Identifiers;
- In-App Purchase Capability in Xcode is ON;
- Your app is submited and approved, so you can start test IAP (not just in TestFlight).
- Just make sure the “Manually release this version” option is set in before submitting.
Good Luck.
Cheers.