MSXML “The system cannot locate the resource specified”

Question

I have a function which uses MSXML to post an XML document which yesterday started failing despite no change being made to the code. The function is as follows:

Answer 1

It turned out to be a networking issue - I didn't suspect this at first as the error was raised so quickly which didn't suggest an issue with the endpoint. The problem was with a rule which had been added (don't ask why) to the firewall preventing communication with the destination address.