This error points to what I said earlier:
gabriel This means that whatever responds to the HTTP/HTTPS request on itsm.xxyy.com is not r3 but some other webservice.
r3 cannot run under Apache as a website, because it is its own webservice. If your Apache is running on 443, r3 cannot.
If you need multiple webservices (Apache & r3) to respond to the same port, you will need a proxy. This proxy would run on 443 and would then redirect traffic based on some rule (like which subdomain is accessed) to another webservice.
