This is a security feature from our sign-in system. It is designed so that another user cannot just enter a player's Salesforce Username and access the system.
To verify the user, go to setup in Salesforce and navigate to users:
Locate the user who needs to be verified and click the Verify link:
Salesforce will send out a verification email to the user and once verified, they will be able to log into Engage using the Login with Salesforce option.