We've just recently installed the Sitecore Publishing Service v3.1.4 and into our 9.0.2 setup of Sitecore. Currently Master to Web publishes work great but I'm unable to publish from Core to Master. Referencing their documentation it looks like out of the box only Master is a valid source within the sc.publishing.xml. Beyond that I'm not sure from the perspective of the Core database how to migrate changes to the Master database.
Any documentation that could help get us past this would be fantastic.