Poor rise while proofing croissants.

Hi there,

I've not made bread with shop yeast very often, in fact I've probably made under 20 non-sourdough loaves; still they have all risen as quickly as one would expect.  I am however having massive problems with getting proofing croissants.

After seeing one of Txfarmer's posts on croissants, I figured I'd give them a go - the recipe and steps are great, and I've not had any problems with the handling or other details.  All goes well until I roll them and leave to proof, they just will not rise at all.  They rise in the oven, and the small amount of yeast in the poolish does develop as desired, so I know that the yeast is not dead.  I have been using Allison dried active yeast, and the proofing temperature was 18-20C; proofing duration has been as long as 6 hours.

So either the yeast is not ideal for the purpose, or I am doing something very wrong.  Not that the results haven't been good, but the lack of proofing is really hampering a more open construction.   I beg thee, veterans of baking - spare my sanity.