emails for registered users are not sent

Hallo ! I'm using the gridbox login plugin.
In the users options (joomla 4 user option) I chose to let them register with a confirmation email, but it doesn't work. No email is sent and the user is immediately approved.
But this is not a big deal.
The biggest problem is that administrators do not receive an alert for a new registered user.
In the joomla global setting the option "send email" is setted to yes
In the joomla user option "send email to administrator" is yes
So I'm wondering if the problem was the login plugin of the gridbox.
Help :-(

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