As an additional security measure, user accounts are limited to three concurrent sessions. A session begins when a user logs in.
If a user signs in to a fourth session, the oldest session will be automatically signed out and this error message appears:

Revoke Access
To view your active sessions, go to Settings Security. You'll see the option to terminate sessions remotely. This allows you to end a session on a device you're signed in to but can't access.
Note: This will only end your personal session on the specified device. This feature does not allow you to terminate sessions of other users. This does not affect user permissions or roles.