I have developed an android app. I am doing Closed testing for release the app to google play store.

I released the app, but testers can not recieve the email.

The status of Closed testing – Alpha is:

And I registerd 20 Testers properly:

Production Status is “Inactive” and the dashboard said Have at least 20 testers opted-in to your closed test 0 testers currently opted-in

I don’t have any idea what I should do.
Please tell me the next step what I have to do.
This is my first time releasing an app on the Play Store.

Anything is fine, so please answer me. Thank you.