Why parsing does not work when you configure a proxy server?

Hello! This problem occurs when parsing the site. Everything works, the script is worth on the open server, but should I configure a proxy server error appears
504 DNS look up failed
The webserver for www1 reported that an error occurred while trying to access the website
the site opens
What's the connection, please tell me what's wrong?
July 8th 19 at 15:37

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