User not visible in list, and also won't add as a new user ?

my question is exactly https://help.zoho.com/portal/en/community/topic/user-not-showing-on-list-but-i-can-t-add-it

i don't know if my email desired address is added as a secondary or not. i want to add

anwar@meritservicesltd.ca and it wont allow me to add and says user already exists in your org.