I am having problems testing my in-app purchases. I get back valid product identifiers, but upon purchase I receive the dreaded \"Cannot connect to iTunes Store\". Interesti
In addition to all the other methods outlined here, if you are working with subscriptions it seems you need to make sure you've generated a shared secret:
"To test or offer auto-renewable subscriptions, you must have a master shared secret or use an app-specific shared secret for each app."
A master shared secret is generated from the 'Shared Secret' tab of the 'Users and Access' section of App Store Connect.
An app-specific shared secret is generated where you manage the in-app purchases of the app itself.