Can't play VST using MIDI keyboard

hi,

just setting up Cubase 7.5

I add a VST (Halion for example) as a Track Instrument

MIDI looks to be all setup OK (can play stuff in Kontakt OK)

I can play the VST using the mouse - but not using the keyboard

Selected All MIDI as the input and HAlion is the output, and when I press a key it registers on the Transport - but does not seem to pass to the VST?

Am sure it’s something trivial…hopefully!

aaaand yes it was trivial… didn’t hve MIDI thru enbled.

I am having the same exact problem, only midi thru IS active. The light on the VST instrument (halion, prologue, etc) lights up when I play my keyboard but no sound comes out unless I use the mouse and pointer on the onscreen keyboard.