Portal for ArcGIS 10.3.1 returns a 404 not found error when attempting to open an Operations Dashboard application from the Portal home page when included in a group shared as a featured content group.
Issue not reproducible with proper configuration following instructions in Deploy Operations Dashboard for a Portal site, http://server.arcgis.com/en/portal/latest/administer/windows/portal-deploy.htm
If this is not performed or is performed incorrectly, opening Operations Dashboard for ArcGIS (Desktop version) will fail with 404 error.