From the manual I can find online, it looks like you have to actually press the power button when the blender portion isn't yet attached. The blue light will come on, and then you attach the blender. After the blender is attached, a green light will come on, and it will run for one minute. If you are using "Souperblast" mode, with the necessary pitcher with a vent cap, then repeat the previous steps and after the light turns green, hold down the power button for a few seconds until the light turns red. That mode will run for about 7 minutes and will heat the contents, according to the manual. I put a link to the manual I looked at below.
If your NutriBullet suddenly stops during use, see the Magic Bullet NutriBullet Stops Suddenly During Use problem page for possible problems and solutions.