Something wrong with pizza dough - 3rd time in a row I was pretty sure I had my recipe and method nailed, done tens of pizzas with it but it failed me now for the third time in a row. It's driving me nuts, I had to throw away dough worth 15 pizzas.

The problem is it won't rise as it should. 

First the recipe, which I took from popular Italian website and translated. I let it proof for 2 hours.

1/2 kg unbleached all purpose flour 
4g dry yeast, half sachet, or 12g normal.
1tsp sugar
11g sea salt, 1tbsp 
300 ml Warm water
3tbsp Olive oil


So, why it wouldn't rise is beyond me. What might be the factor?

1) Is it the brand of the yeast? Now I use Red Star, but I used some European before.Both fry yeast in sachets.

2) Too cold or too hot water to let the yeast soak (proof)?

3) Kneading for too long or not long enough?

4) Room temperature for proofing too low? It is winter now, and all the previous attempts were in summer. Although I did place it near the heat source.

Last thing I'm going to do now is I'm going to increase the amount of yeast by 2x, to see what happens. But originally I had to reduce by half from all the US recipes when I found an Italian and it worked much better. I still have to know what has changed in the overall conditions for such a huge difference. 



UPDATE

Left it overnight and the dough seems perfect. It just needed more time it looks like.
There is not enough information here to give you a solid answer.

There are two things to consider:


Have you proofed your yeast?  Active dry yeast needs to be proofed, and while instant yeast does not, it cannot hurt.   Dissolve the yeast and sugar in warm water (about 105 - 110 F, 40 - 43 C).  After 10 to 15 minutes, it should be quite foamy.

This demonstrates that your yeast is alive and well, and will be ready to raise your bread or dough.
In the winter, rising will be slower, possibly by a lot, depending on how much cooler your kitchen is.  You may wish to create a friendly proofing box for the rise, with a warm hand humid environment.

My favorite way to do so is to boil a microwave safe container of water (a couple of cups or a liter) in the microwave, and then push it to the back of the cavity.  Then use the microwave as a place to let your dough rise. The microwave has to be turned off while proofing, if you turn it on, the dough will fail.