Issue with "Add Your Mobile Number"

Issue with "Add Your Mobile Number"

Hello,

I am trying to sign up for email service for a domain name, and I cannot finish the authentication.  When I enter my mobile number, I receive the message "We’re unable to send OTP to this mobile number. Please contact support-as@zohocorp.com".

I sent an email to this email address 4 days ago but have not received a response.  Please advise how I can proceed with setting up email service.

Thanks