"This project isn't available" occurs when selecting Reports>All Reports.
We have the online version of JIRA Agile and since the update which occurred early this morning (Jul-6-2015), we are having issues trying to see the "All Reports" page for a board that views 2 projects.
I can select all of the individual reports ok, just not the "All Reports".
jul6_15_allreports.jpg
The error message that appears would indicate some sort of issue with the permissions, but this happens on a user with admin privileges.