Fitbit app problems

I don't have a Fitbit device but for over a year now I've been using the Fitbit app to track exercise, steps, calories etc. and I've been really happy with it. Ever since the update that came right before the new iPhones released the app has not tracked any of my steps! I have the new iPhone now and it's still not working. Anyone else having this problem and been able to fix it? And yes I have allowed Fitbit to use the motion tracking on my phone. I also have Fitbit connected to the health app but it's still not syncing!