OK. I’ve just verified the problem IS Cubase 7.5.30 (7.5.20, 7.5.10 …). I connected my Mackie MCU 8 to another PC .
Using PowerTracks Pro 2012 (AKA PTW. It’s not compatible to the MCU 8 so, the Transport features & Track Led aren’t supposed to work. But the MIDI Pass-thru is compatible if the MCU is working). Both of my MIDI Keyboard Controllers (MCU 8 is a Hub function for these 2 KBs) are working as supposed to.
In my Cubase 7.5.30 DAW, my MIDI signals are not passing through to Cubase- dead, nothing.