Hi Dilip,
What is the error that you are getting when you are trying to download the FTP catalog? Please make sure that the internet is accessible and the proxy settings are enabled and set at the preferences page in OME.
To add to this, even for FTP catalog, we need to make sure the software inventory table for all the servers and RACs is populated after discovery and inventory so that you can create a local repository out of it. If the software inventory table is still not populated, i reckon it is better you call the support number so that they can look into the configuration.