777 error is usually a connection timeout error. It is an error that can occur when you are using an online application/website that requires a user to Sign In. In these cases, the system is in a session and can timeout and cause the browser to get “confused.”
As a general rule, this error is a non-fatal error and can be caused by many factors outside of TeamUnify’s and the clients control. If the problem persists, please close all browsers and restart. TeamUnify strongly recommends Firefox as the browser of choice. It’s free and available here.