Evandro,
There was a bug fixed in v4.2.2 that was preventing the new user emails being sent to administrators, which explains why you're getting them now. JFBConnect uses the com_users language file to pull the right string out to send to the admin in an email. I'd check that the en_GB.com_users.ini file, or any other language files that could be used on the front-end for com_users, has that string in there.
Alternatively, if you'd like to not receive that email, I'd recommend editing your Admin user in the backend and set "Receive System Emails" to "No". Any user with that enabled will get system notifications for new users or other events.
Hope that helps, but if you need anything else, just let us know!
Alex
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