Unity Cloud DevOps does not let me assign my last available seat (1 available, 2 used)

Hello All!
I have been trying to assign my last available seat in the Unity Version control, I have 1 available seat, nevertheless when I try to assign it shows the following error message:

"You have already assigned all of your available seats. Upgrade anytime to purchase more seats. "

I sincerely don’t know what to do, the platform clearly shows the available seat but the system won’t take it.

The user I want to add is correctly added to my team.

Thank you for all the help you can provide to fix this issue!