HRESULT 0x801901F9 (HTTP_E_STATUS_VERSION_NOT

Status / error code:

Category:

Constant name:

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Facility:

Operating System:

Description:

The server returned HTTP 505 HTTP Version Not Supported.

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HTTP_E_STATUS_VERSION_NOT_SUP

HTTP_E_STATUS_VERSION_NOT_SUP maps to HTTP 505 HTTP Version Not Supported. The server does not support, or refuses to support, the major HTTP version used in the request message.

What to check

Verify the negotiated protocol version and whether the failure occurred through a proxy or direct to the origin.
Check client support for an appropriate protocol fallback and the server or gateway configuration for HTTP/1.1, HTTP/2, or HTTP/3.
Do not treat 505 as a TLS certificate or TCP connection error; it is an HTTP response from a server that parsed the request sufficiently to reject its version.

RFC 9110: 505 HTTP Version Not Supported

RFC 9112: HTTP/1.1

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