The ftp server is still working fine but it has only versions up to Cubase 6. All versions from 7 to 9.5 are not accessible at the moment when your current version is V10.
If it’s no possible to add the old versions to MySteinberg then at least add them to the archive on the FTP server.
the full installers for Cubase 7.5 through Cubase 9 are accessible from this page:
Selecting ‘Cubase’ from the ‘Unsupported Products’ drop-down takes you here, where you can download the full installers for all previous versions: Cubase | Steinberg
The Cubase 5 ISO is missing, maybe overlooked.
fyi:
The ftp site contains updates and content installers.The only full installer there would be the Cubase SX3, the last version of Cubase that can open Cubase VST files.
The links I posted give you access to all full installers and updates starting with Cubase 4, except Cubase 5 (surely overlooked). 7.5 to 9 in ‘Downloads Software’ and 4 to 7 under ‘Unsupported Products’. 9.5 and 10 via the Assistant of course.
Previous versions are mirrored from the ftp and indeed don’t contain the full installers. Will ask about the possibility to add them, too.
The ISO for Cubase 5.5 is here: http://support.steinberg.de/ISOs/Cubase/Cubase_5.5.0.602.iso PC and Mac.