I am getting the exact same issue, I found this worked perfectly on the previous version of OME but is now failing. Also discovered that when trying to deploy firmware to blades on the old OME, there was a port 892 required but this was never mentioned in the documentation. Had to run firewall traces to get this information. I have opened a support case about this, the funny thing is that I can download catalogs on another instance of Dell OME at a different site using the OVF template. It is using the exact same proxy info but on another site (that was working on the previous OME version) it is failing now all of a sudden after the upgrade. Same issue at 77%.