If you've invited a team member and they appear as "In another organization" in User Management, it means they have created their own organization instead of joining your team on Salestrail.
To fix this, the steps are very simple:
They need to log into the Call Analytics dashboard.
navigate to User Management
Click on their name
Delete themselves from the organization that they have created.
Log in again and they should see that they have an invitation to the correct team.
Complete the sign in process.