Unable to manage domain: stuck at step "Add Mobile Number"

Unable to manage domain: stuck at step "Add Mobile Number"

When trying to configure Zoho mail, I'm redirected to the page
"Add Mobile Number
As a security measure, you need to link your phone number with this account and verify it to proceed further."

I'm not able to enter a phone number at this step. The form never accepts my phone number / password.

How can I proceed ?

Please note that my account has already a phone number linked, and has 2 factor authentication enabled.

Thanks for your help !