I cut the dead wood back in the center when it was leafed out - in May - there are no flowers at all and many of the leaves are yellowing the plant is about 4 year old help
So, the center of the plant was dead in spring. Do you mean regular winter kill? Did you remove more than half the plants leaves? You may have just really stunted its growth for this year. Make sure it is getting enough water and only use a side dressing of compost, not fertilizer. Caryoptersis blooms in late summer to early fall. It is said to tolerate summers in zone 9 so if you are having a zone 10 type summer, it may be heat stressed.