HTTP 1.1 426 Upgrade Required

[addsum]

Client site suddenly getting the message above and we are able to duplicate the same issue  in our development environment.  Have tried a number of things to try to get past it, but no luck so far.  Hasn't something changed?   Is HTTP 1.1 protocol no longer available?   Snippet from a trace is below.  Connecting to Trello via a desktop program that has been in production and in active use for a long time now.  Using Nov. 2018 openSSL DLL files.   Tried using only TSL 1_2 as suggested by a 2019 post which we were already supporting but still receiving the same response.

Trace file snippet:

HTTP/1.1 426 Upgrade Required<EOL>Date: Thu, 20 Aug 2020 18:07:35 GMT<EOL>Server: globaledge-envoy

[addsum]

Forcing the call to use 1.1 seems to resolve for now.  Something must have changed in the last couple of days.

[bentley]

HTTP 1.0 has been removed.

> Is HTTP 1.1 protocol no longer available?

HTTP 1.1 will continue to be supported for the foreseeable future.

[Vincent MARTIN]

I confirm that forcing HTTP 1.1 also solve my problem. Thx for the hint.