Besides making the trust, I have seen:
No JIRA Projects available in Confluence
Error
Making a JIRA Report, no projects were available, giving me this error i atlassian-jira.log:
2014-03-13 07:42:16,081 http-bio-6060-exec-47 WARN anonymous 462x2065249x1 - 77.243.49.62 /rest/api/2/project [auth.trustedapps.filter.TrustedApplicationFilterAuthenticator] Failed to login trusted application: confluence:1838577 due to: com.atlassian.security.auth.trustedapps.InvalidCertificateException: Request not allowed to access URL: /rest/api/2/project
Forencics
Examining the allowed Urls, I found:
/sr/jira.issueviews:searchrequest-rss /si/jira.issueviews:issue-xml /sr/jira.issueviews:searchrequest /secure/RunPortlet /rpc/xmlrpc /rest/api/2/project
Solution
/sr/jira.issueviews:searchrequest-rss /si/jira.issueviews:issue-xml /sr/jira.issueviews:searchrequest /secure/RunPortlet /rpc/xmlrpc /rest/api/2/project