"You do not have permissions to create this account in Zoho Mail" - Please Help

"You do not have permissions to create this account in Zoho Mail" - Please Help

Hello,
I just signed up for the zoho mail for my domain and I am unable to add users.
I am getting this error: 

You do not have permissions to create this account in Zoho Mail. Reach us at support-as@zohocorp.com for further assistance.

Also I am unable to edit/change the First Name or Last Name of the already created emails. I am getting the error: Ooops! Something went wrong, please try again later.

I want to add two emails for my domains. Please help me.
Thank you.