CelloSaaS provides a configuration level settings which will help you to either Enable/Disable concurrent logins from multiple system.
To Enable or Disable
In App Settings, if you set the EnableUserActivityTrace as True then same user can't login form different machines.
<add key="EnableUserActivityTrace" value="false"/>
This is an application level setting and not Tenant level.
User must properly log-off from the application other wise he can't login for next x minutes.