Cannot add 10th member to a trello workspace

[Matt Barnes]

Hello

We should be able to add 10 people to our workspace but my colleague is getting this message?

"You can't join this board. 

The invitation link may have been disabled or this free workspace may have reached the 10 collaborator limit. Try contacting the person who sent you the link for more info". 

These are 9 users right now - 

[Daydreamer Mike]

First step, go to the workspace > members section and check the number of collaborators you have....