I had the same problem with R620 two days ago, solution that worked for me was going into bios -> iDRAC setting -> reset to default (be sure that you have Service Tag cause this could erase ST number). Good luck!
When I attempt to update the firmware via Licecycle ctonroller FTP option to simply the default of 'ftp.dell.com' all I get is "Connecting to FTP server to download the catalog" for about 5 minutes and then a failure (see attached image). Is there a trick here to get this work? No proxy server and the network is open to go out. No proxy, and just specifying the feault 'ftp.dell.com'. [IMAGE] 
Lifecycle controller FTP Firmware update failing