How to use HttpClient (C#) to open certain sites?

Question

C++ / C#

HttpClient (C#) won't open some sites like spys.one.
An error is either 503 or 502. Everything is fine in the browser.
Tell me which way to look?

Answer 1

Usually 5xx errors indicate a problem on the server side. Those. you can't do anything in this case.

Answer 2

In my case, it looks like it's in the title. It was necessary to set the
UserAgent header of the request, as in the official instructions it says:
" https://docs.microsoft.com/ru-ru/windows/uwp/netwo... "
questions
Thank you all for the answers, there is room to move on.