Janni,
Mine also did the same thing I think, it grew all last year and the temperature dipped a little too low for it.. I believe the lowest it was was -9 C
Which I was reading that -10 can fry the ends of the vine and therefore it will not bloom the same year.
What I ended up doing was cutting the dead parts of it off and leaving the partially-growing ones on.
I hope that mine blooms next year..

I would not prune it to the ground unless you have vines coming up from the ground and nothing at all on the dead stuff. It might not be dead yet though.

I do not grow montanas, they get too big for my yard but they are all over this area. I see some up in trees that I don't think have been pruned. I see them in yards that clearly do not have a gardener living there...