Not able to add .co domain in Zoho

Not able to add .co domain in Zoho

Hi there, I'm not able to add my domain hifigadgethub.co in domain verification step. 

It keeps getting the error Oops! Invalid domain detected by the system. Please contact <a href=mailto:{0}>support-as@zohocorp.com</a> for further assistance.

​

Please help!

Here is my Zoho User ID: 819341389

Kind regards.