Hello!
I've linked our Confluence and JIRA (OAuth, Trusted Application, IP whitelisted, to and fro), from Confluence the JIRA macros work beautifully, I see Confluence edits on my JIRA dashboard's activity stream, however ... I can't add a Confluence page to a JIRA Issue, because I get the: No Confluence page found with the given URL. error message. Both products are hosted on the same server via the standard bundled Tomcat, they listen on different ports and they are both reverse-proxied via nginx (which does SSL termination too), but the Application Links are set up via the direct port numbers and the displayed URL is configured to show the proxied URL. (This URL shows up when I search for a Confluence page in JIRA, I can select it, but linking fails.)
JIRA runs v5.0.x, Confluence is at 4.2.x.