TestFlight Issue With Invitation

I have successfully invited my internal testers to test my 2nd build, and they have both received the invite email. The problem is that when they click on the invite, when they are taken into TestFlight they get a message saying the app is not available. If you have any experience with this or know how to fix this please let me know. I think the pictures below will be very helpful in finding my problem. enter image description here

Solution

Make sure beta testing is turned on, or try turning it off and on again.