When Editing Wiki Pages (in this case, in the "Training Project"), the page cannot be saved due to a lack of licenses:
"""
This Confluence installation is not licensed for additional users
You have exceeded the maximum number of users for your license. You will still be able to view content, but in order to create or edit content, you must reduce the number of active users in the installation.
There are two ways to reduce the number of active users:
Disable users
Delete users
To disable or delete a user, visit the Manage Users page then search for their name. After following the appropriate link you can choose the 'Remove' or 'Disable' option.
"""
Although, we just have the right number of users on our Users group.