Daily digest shows "sent" but did not reach anyone

I have installed the plugin, created an email called configured to send a daily digest, and have 20 subscribers only.

After posting 7 posts the time for the daily digest came, but the email never reached the subscribers.

I sent several test emails using the "send test email" option, and it arrived successfully, but the daily digest did not reach anyone.

In the "sent emails" tab, the email is shown as "sent" in front of all the subscribers, and there are ZERO errors found.

I went over the configurations so many times and I am sure that everything is configured correctly, but the email has not reached anyone.

The next email is due after a few hours. Please help.

Atef Raouf