Hi Mike,
Thanks for your reply.
I have now un-proxied my domain at CloudFlare, but that doesn't seem to have made a difference. I don't understand the option you're talking about here, but I don't know if I can use it as I have to provide certificates for the domains to Esri consultants to configure into the ArcGIS Enterprise application we're deploying. How can I get this to work?
Thanks,
GAM