Why has my Cirrhosa not flowered.

Took me a while to realise you were talking about Clematis cirrhosa! I've only grown one of these before - my experience was it didn't live up to the hype about it. I found it a weak grower, with little flowering, though it was in a fairly shaded spot, which was why I chose it, it being said it does well north facing.
That said, I assume yours is not in a tub or pot? If it is, they don't do well in pots. If its in the ground, then water may be an issue, and it will need feeding or fertilising in the spring and early summer. Hope this helps, but I expect you can tell I'd not recommend this plant to anyone;-)

Hi Windmill. Just out of interest, how would you describe the health and growth of the foliage?