Same thing happened to me. My app went through a few rejections that I resolved. Then my app was approved but the subscriptions are in waiting for review state and not working in the app. Will try calling them tomorrow (during business hours) and report back.

This issue went away for me once my developer account payment was fully processed and my account came out of the (Pending) state, so I believe this issue is a result of being in the pending state of a developer account while trying to access app store connect.

I have the same issue here, and I just signed up for my developer account a couple of hours ago. Looking at my developer account now, and noticing it is still in the (Pending) state, with a message on the main page at https://developer.apple.com/account/ "Your purchase may take up to 48 hours to process." My guess is the links aren't activated until this process is complete. Will check back in the next couple days to see if the issue is resolved.