I am enabling AD authentication in our system however when I try to enable AD login for a user I get the error "No more support reps available for your license". I am able to create a standard login for the user without any issues, and we are currently only using 13 out of our 20 support reps we're licensed for. 

If the user has a standard login and I try to enable AD authentication for them I get a blank error, so I remove this first and then try to enable AD. 

running the below query i found from searching similar issues it confirms I've only got 13 active users

select * from aaauser aaau join sduser sdu on aaau.user_id=sdu.userid inner join helpdeskcrew hd on sdu.userid=hd.technicianid  join aaalogin aaal on hd.technicianid=aaal.user_id