furrywombat - Looking into this. Are you able to directly browse the api using https://www.methodintegration.com/methodapi/service.asmx and invoke a function?
Manish, Paul,
Every function call works fine. I'm getting valid XML response.
This is almost definitely an issue with a blacklisted IP address on your end. I am sending you AND Paul a private message with some information that will help you debug.
We will surely look into your message and make it better.
Cheers!!