Here's what it should say underneath the xml, see the below screenshot... So here's my suggestion, go to your webhost (hopefully) then ask NICELY

to ensure that xml_rpc is compiled into PHP show them the screenshot below...
I can't help you out there, as I don't own the server or host your site, but in today's age I would suggest that any host have xml_rpc compiled in to allow their clients to host sites that have webservices that require this....
As you know, they "may" give you some excuse on why not, and if that's the case it's time to find yourself a flexible and very reliable webhost.