Maximum number of users was exceeded, this license allows 10 users for limitation type 'NAMED'

Hi,

we have a access to create 10 user into our enviroinment but just after creation of four users it's not allowing me to create another required users. even i deleted existing Demo user also.

as per environment log message "Maximum number of users was exceeded, this license allows 10 users for limitation type 'NAMED'",

while clicking on Add user button into relevant  Group it is showing pop-up error message "An error has occurred while handling the request."

thanks