How do I redeem another code for TestFlight

Hello Boomtool-21,

Thanks for asking the Apple Support Communities about TestFlight.

This is a developer app. You can reach out to the TestFlight team here: https://developer.apple.com/testflight/

Or look at the info here: https://testflight.apple.com

We'll also ask the moderators to move this to the Developer queue for more help. Cheers.