Some Adobe Bulletins are failing to download in Patch Management while other Adobe updates download successfully. The problem updates can even be manually downloaded on the NS by opening their download links such as: ftp://ftp.adobe.com/pub/adobe/reader/win/AcrobatDC/1501020056/AcroRdrDCUpd1501020056.msp

The problem Adobe bulletins use FTP download links instead of http download links like other Adobe bulletins. Patch Management connects to FTP anonymously (unlike a browser) and actively (requires more ports than passive FTP) and this is blocked by most firewalls. 

Whitelist the following address in any firewall that the NS is trying to communicate through: ftp://ftp.adobe.com/*. Also ensure that the firewall allows Annonymous and Active FTP communication. Wireshark captures will often reveal why a firewall is rejecting FTP access.

More information is at Ports and Protocols for IT Management Suite.