To make the icon appear please follow the steps below:
Go to the Members section
Search for the affected user
Once you found him click on the 3 dots menu on the right side of his name
Select Manage roles
Set ConQuest to No Access
Click Save Changes
In the Manage Roles click Close
After you've followed the steps above, you can give the user the permissions back and then inform the user to log out and wait for at least 10 minutes. ConQuest should now appear in the menu.