Testers could not download app from Firebase App Distribution

Question

We pushed iOS app to Firebase distribution and sent invitations to every tester. Our testers followed all steps and get ready to test the app. Unfortunately, the testers get

Answer 1

As I'm using the service for the first time, I initially thought I didn't understand how it actually works, or it was too stupid to be true, but then it actually behaved as expected. My first experience worked like this:

1. I exported my app with my current provisioning file (Developer, not Enterprise) and uploaded it to firebase distribution (1st time).

2. I sent to my testers a link to download and install an app that they can't use because their device UUID is not registered in my provisioning file.

3. I got a mail with their device UUID of my first tester and add it to my provisioning file.

4. I exported again the app and upload it again (2nd time).

5. It created a new distribution so I sent him a second link to download and install the second version that now should work.

6. My second tester accepted and I received a second mail..added, exported and uploaded (third time).

7. This time on console it show a big blue rectangle with the message that the version was updated with new devices and testers will be notified by mail. ( this is how I actually expected it to work ).

What can have happened on my 2nd upload? Would an Enterprise certificate avoid all this device UUID registering part?