My IOS app has in-app purchases. I need to test my refund handle flow.

I have one sandbox test user that I've set up on app store connect for my app. This account has made many purchases for the app running on a real iPhone. When I made the purchases, it asked for this test account's email and password, so I know that the purchases were made through this account.

I have tried to find the purchase history for this user on app store connect. It's not there. It merely shows the date of last purchase and the option to clear its purchase history.

I have tried logging into https://reportaproblem.apple.com/ with the test account. It does log me in, but immediately gives this error:

You must use an Apple Account that has previously been used in the store. Sign in again with another Apple Account.