Hi, since I am using a Virus TI myself, here is what you may(!) want to try in a very first step. Connect Octopus directly to the TI via MIDI and put the TI in sequencer mode (each part listens to that one channel). This is a good setup to get acquainted with the machine and get a feel for how the MIDI channeling and program changes work – and in many cases quite sufficient for a nice performance and a good source for quick gratification 
In the next step you’ll have to look at the way Live is treating the MIDI stream coming from Octopus. You’ll have to make sure that you route the signal to the right place, i.e. wherever and however your TI plugin is listening. Otherwise you’ll have to let us know more about the way you have set up your Live set.
Cheers,
Gabriel