I used to have this problem until I switched yeast. I was using the 3-pks of dried yeast which were always hit or miss in terms of rising. I now use the dried yeast that comes in the 1 lb pkg – usually the Gefen brand. I keep it in a sealed tupperware container. I have never had a problem since I switched. I put all the Water, Sugar and Yeast for the recipe into the mixer and let it sit for 10 minutes. If the yeast is good – it should start bubbling.
My recipe is:
4-5 Cups Warm Water – the more water the stickier the dough but the lighter the challah
1 1/2 – 2 C Sugar
4 T dried Yeast
Combine the above and let sit for 10 minutes
Add:
4 Eggs
5 lb bag Flour – High Gluten preferred
1 C oil or ( 1 stick Margarine + 1/4 C Oil)
4 T Kosher Salt
Let double – punch down and braid. Let rise again for 30 min and bake at 325-350 until golden brown.