Jetpack and the xml_rpc-32700 issue

I have two websites on the same host:

https://www.herding-dog-training-border-collie-sheepdog-dvd.com
and
https://www.workingsheepdog.co.uk

BOTH have Jetpack installed, but on https://www.workingsheepdog.co.uk I get the xml_rpc-32700 error when I try to connect to wordpress.com. (Jetpack is working fine on the other domain).

I’ve disabled all plugins, cleared the cache and even downloaded wordpress and uploaded a squeaky new xmlrpc.php file.

Still I cannot connect.

When you read the blurb about WordPress, it gives you the impression it’s all going to be simple and plain sailing, but it isn’t is it? Sometimes it’s a nightmare.

I’m at a loss to know what to do next to resolve this.