I started to see errors on our calls to the Xero API, with status 412 returned. The initial clue was in this Xero Community post.
On windows 7 machines or older machines, you may need to install a fix to ensure that windows can handle TLS 1.1 or 1.2. I usually recommend this update as a first step as it mitigates not knowing how the underlying code, wrapper may work.
This led me to a post about TLS versions, with a useful piece of code to check the TLS version of your server:
<% Set objHttp = Server.CreateObject("MSXML2.ServerXMLHTTP.6.0") objHttp.open "GET", "https://howsmyssl.com/a/check", False objHttp.Send Response.Write objHttp.responseText Set objHttp = Nothing %>
Running this I found the particular VM was showing TLS1.0, which is not good. I recalled I’ve seen something similar a few weeks ago on another project which was calling the Vimeo API, which now requires TLS1.2 or above.
This particular server is 2008 R2, and there’s a patch to upgrade your TLS to 1.2.
Now the TLS test code above is returning
And my calls to the Xero API are working.