Domain validation in mautic.net

How can I validate a sender domain?

I go on mautic.net, then edit and compile the form “Domain Optional” with my domain in the mydomain.com format, I save it but nothing happens.

I had the messages “The domain xxx.mautic.net was successfully updated” but I can’t see the red button “ValidateDomain”

Where am I wrong?

How can I validate a sender domain?
I go on mautic.net, then edit and compile the form “Domain Optional” with my domain in the mydomain.com format, I save it but nothing happens.
I had the messages “The domain xxx.mautic.net was successfully updated” but I can’t see the red button “ValidateDomain”
Where am I wrong?