I'm trying to add In App Purchases to my app so I set up a sandbox Apple ID with one of those [email protected] types of emails. I also copied the password from Notes straight into App Store Connect, so it's definitely not messed up there.
I got the verification email, I verified, then I tried signing the Apple ID into the simulator using my app. I typed in the details at the point where the fields in that alert comes up, I press ok, then nothing. The box disappears and nothing comes up. I tap the button again, then the Apple ID prompt shows up again.
Then I tried it in Settings by going to "Sign in with your Apple ID" and typed in my Apple ID & password in there, and I got a message saying "User name or password is incorrect."
I tried setting up another sandbox account with a different password format, got that verified, then the same thing happened.
How do I get this working correctly and sign in properly? I obviously need to test these things before I launch.
I fixed it by logging into iCloud.com once using the sandbox account, then signing into the iPhone simulator.
(I tried accepting this answer, but it won't let me for 2 days :/)