I had plants that were grafted and callused in februrary, that didn't bud out and start growing until yesterday. I had given them up for dead and basically ignored them from march till now-they're fine, just slow. Some will always do that.
I had many vines that were destroyed by a family member's dog that was staying with us. chewed off at the ground, or ripped out of the ground completely. Some of them are growing back now, two months after budbreak. Even the shards of chewed and crushed vines that I stuck in pots and ignored have started growing roots and shoots. It just takes time.