Disallow Concurrent Logins by an Admin
You can ensure that an admin can log in to a tenant only once, instead of being able to log in to a tenant multiple times concurrently. The default setting currently allows concurrent logins.
To disallow concurrent logins:
To change the default, go to Settings > Administration > Admins.
On the top right-hand side, click the Tools icon to open the Configure dialog box. Activate Disallow Concurrent Logins by same Admin.
Click Save.