What provision and certificate combination do I need to test leaderboards on a Test Flight release?

I have been trying to set up Game Center specifically for the leaderboards and achievements will no success. I have done work with leaderboards and achievements for android devices with no issues. I am not sure if I am using the correct certificate and provision combination or if I have something configured wrong in app store connect. I have tried creating a sandbox tester however I may not have used the account correctly for testing. IOS is new to me and any help would be appreciated. I have googled just about every single thing possible and looked through the docmentation to no avail. At this point I'm just going to hope it works once I submit it to the app store.