Hi,
Since you are calling the service from a different server, the settings in Liferay are not relevant. There are two things which are relevant:
1. Whether the service are open to the outside world.
I think you have done this properly already, assuming that you are not doing a POST or a DELETE. For reference, by default Form Runner services are protected, and here is the doc:
https://doc.orbeon.com/xml-platform/controller/authorization-of-pages-and-services.html2. Whether you are providing, when calling the service, authentication headers which are accepted by the service.
The same headers which you configured to map Liferay headers should be passed.
Does this help?
-Erik