This tutorial explains the HTTP Error 407 Proxy Authentication Required error, what causes it, and how to fix it. The following error can cause website downtime, which may decrease the website’s reputation and make clients unsatisfied. The HTTP 407 Error typically occurs when the client cannot auhenticate with a proxy server. Similarly, when the proxy server cannot allow access to the requested resource without authentication. Identifying the root cause of this error can be difficult but we will show you a couple of possible solutions.