What does 511 server error mean?

511 Network Authentication Required. This response is not sent by the server to which the request was intended, but by the proxy server - for example, the provider's server - in case when the client must first authenticate on the network, for example, enter the password for a paid Internet access point. It is expected that the body of the response will return a Web-based authorization form or redirect to it. It is introduced in RFC 6585 Draft. How to fix it? 1. Contact the hosting provider's technical support;
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