Hi @Olivier - This is by design. While the Free Plan does allow unlimited team members, in return you are limited in the number of active/editable boards as well as other features. Now that you have the Consultant Plan, you do have more features available to you. Here is a good comparison of Plans and Features.

Day Passes or Guest Editors

Because adding team members to your Consultant Plan team would require them to have a paid seat in order to be able to edit, you now have two options:

1. Day Passes - I will let you read up on this option and focus on the second one:
2. Guest Editors - You can invite users to edit boards using the Guest Editor feature. While the setting is → Anyone with the link Can edit, you can also password protect the board - note: you may not yet have this ability on your account yet:

ok thanks and i ve seen after with the guest editors to allow to write post it or cards. Thanks a lot 

I’m waiting for the protect board password to consultant so ;) 

have a good day