I too was having this problem. There are a few things I have tried and seem to have worked.
1. Hard start your tracker by holding down the left button and the lower right hand button together until you see the fitbit logo
2. Make sure your HR is set to ON and not Auto, (this will drain the battery if left this way). but it seem to only work correctly this way for me. I find that keeping it on Auto the led lights turn a very light green and the if I tap the blaze it shows bright green.
3. I have change the setting to nondominant hand but keeping the blaze on the dominant hand on the phone app.
4. Make sure your bluetooth is connnected to the blaze.
Since doing these changes I have been receiving the sleep stages consistantly since July 20.
Good Luck
