When a user is member of the "administrators" group but not a member of the "site-admins" group then they cannot access the user management.
The link is still displayed in the administration screen, when the user clicks on the link then he'll be re-directed to the login screen.

Steps to reproduce:

• create a user account and provide membership to the user group "administrators
• login with this account and press the cog -> user management
• Press the button "Leave Jira to go to user management:

You will be prompted with the login screen, no clear error message is shown.