Close TestFlight. Open the email invite, tap “View in TestFlight”, write down the code somewhere safe. Then open TestFlight again and you should be able to see Shadowgun War Games at the top of the list. Tap Redeem and enter the code you received in the email invite.
You’re signed into TestFlight with a different email address than the one you used to sign up for Beta. Try logging in with a different Apple ID.
Goblins and sharks. Please contact our support team and we’ll get you sorted out.