Yes, I think it is worth trying different repeat values.
If the iTach is working with other devices then I think it is safe to eliminate the possibility that the emitter is damaged.
Obviously it makes sense to test the iTach with as many devices as possible and to familiarize oneself with the iTach software before trying to use it with VoxCommando. Solving one problem at a time is always the best approach, IMO.
Once you've established that the iTach is able to send codes correctly, you need to make sure your emitter is positioned correctly (at the correct angle and not too far away - some devices have a better range than others), and then try whatever codes you can find that might work with your device, and experiment with repeats. Usually a repeat of more than 2 is not necessary AFAIK but you could always try 1, 2, and then 3 repeats, and then move on to the next possible code-set.