Today makes twice that I've tried to make brioche and twice I've failed. I have some suspects:
Kneading-I don't have a stand mixer and mixing everything by hand, and perhaps I'm not kneading well enough. ¿Would poor kneading prevent the dough from doubling?
Yeast-I've tried dry active yeast and instant yeast. I mixed the dry yeast with water. And the second time I made brioche I mixed the instant yeast with whole milk heated to 99 degrees F and then I let it sit for 20 minutes; this was 4.5g with 0.5 cups of warm milk.
Overall, I have a feeling it's the kneading. But I dunno.
Best Answer
From your comment that the dough does not rise at all, it is almost certain that your yeast is dead.
Poor kneading will not cause the dough not to rise.
I suggest proofing the instant/active dry yeast in lukewarm water to isolate as many variables as possible. You can even use room-temp water.
Add 1/2 teaspoon of sugar to the water, add the yeast, mix it well and wait for it to start to foam up. There will be no doubt about the foaming - it will foam up like thick root beer. If the foaming takes significantly longer than 10 minutes, then you will need new yeast because the stuff that you have is mostly dead.