The import set up at Midi device manager is broken.
When I click “Import set up” to load a panel previously released (Cubase 8) the result is a list with the same name for all instances (Midi Device instead e.g.Yamaha AN1x) and don’t import a thing!
Update: Exporting the actual set up and try to re-import devices causes the same issue so the export set up seems to be broken too.
I have exactly the same problem. Cubase pro 9 won’t see my previous midi devices from version 8. These are the actual device panels I’ve programmed (not standard midi connections). Anyone know how to get them back? Import setup doesn’t work!!! I still have version 8 running, and there’s still no problem there…
Here’s the workaround…(On a Mac, anyway, but there is a similar workaround on a PC, but don’t ask me where to look for the files…)
Go to (user)/library/preferences/Cubase 9 and replace the file ‘Midi Devices.bin’ with the same file from the Cubase 8 or 8.x preferences folder after re-naming for safety first.
It works, but import/export will still need to be fixed with a proper update
But I did not have the 8th version. Without import MIDI device for me Cubase works on 70%! And this is a serious trouble for me. Since I have a 5 Hardware synthesizers. And I was a very long list for the job.
just posted on the general C9 forum…
i can confirm the same issue here 
thank worked for me on windows…just imported the midi device xml i needed to cubase 8.5 and replace the midi device.bin in C9