A user limit has been set for your Stager account. On the Settings - Account - Billing page you can find how many users there are in your organization and how many users you can still add.
User Limits:
Ticketing: 5 users
Cool: 10 users
Awesome: 50 users
It is not possible to be logged in with the same user on two different devices. If you log in with the same user on another computer, telephone or tablet, the other computer will automatically log out.
There is one exception: When things are busy at the venue, you want to be able to scan tickets with as many people as possible and ensure that everyone is quickly inside. Therefore, for scanning on a mobile device, it is possible to have multiple active logins with one user. This happens when you scan with the Stager scan app.