Thanks @Pranay for the quick response. Just to clarify my understanding, I created one admin user. User creation was successful. I can login using that user. Now if I try to create one more user from login page "Create an account" link, I can see "You are not allowed to create an account. Please ask your admin to send an invite link".
From this message and your response, I can assume that second admin type or any type of user creation is not possible from "Create and account" link. Please confirm.