Hi Frank !
Since 01.Apr.2016 a download is no longer allowed with an "outdated" SAP Download Manager.
Please have a look at note 2282338 .
SAP explains the neccessity of an update to a newer version - currently 2.1.143 is being offered.
The note contains a link to the download section:
Download Manager | SAP Support Portal
It differs from the one I knew and formerly used.
Good luck!
Best regards,
Arved Pohl