If you have increased the number of signed-up users in Confluence beyond the limit permitted by your license (say through JIRA user management), Confluence will cache/remember the fact that you now have too many users. It will do so for the duration of one hour before this result is recalculated.

In this time, users will not be able to add or edit pages. Instead, they will get this warning:

"You have exceeded the maximum number of users for your license"

Please note that even if you subsequently try to reduce the number of signed-up users below the license limit, the cached result will still hold.