407 error message means you have not authorized your internet/server IP address in the Dashboard or you are using incorrect login details if username authentication is enabled.
Authorizing IPs: This can be done from the "Account" tab in the Dashboard
Click on "Account" and then "Authorized IPs"
2. Username and Password: This can be done from the "Account" tab in the Dashboard
Click on "Account" and then "Authorized Users"
NOTE: The username cannot be changed
Allow 30 minutes for the changes to take effect and then use the proxies