Charge 4 not tracking Heart Rate Zone accurately

[Steven76]

Hi, I’ve had a charge 4 for over 6 months and I have a long standing problem with my heart rate zones. I’m using the recommended Heart rate zones based on the app (107/133/165) which seem accurate given I’m 45 years old 

https://ibb.co/gMWgSfK

the problem is that these don’t seem to be synced to my charge 4 and don’t show up when I exercise. I need to get to about 125 bpm to show as “fat burn” on my charge 4 and around 155 bpm to get to “cardio”.

my app seems to be a mix of the two, it shows the personalised heart rate on the graph, but it’s clearly not logging enough fat burn zone minutes given the graph in the link shows a 28 minute workout and I only logged 7 zone minutes. 

https://ibb.co/Pxqyjv3

My charge 4 and iOS app are both up to date so not really sure how to solve the issue. It’s very frustrating, I know I’m still working hard and getting the right amount of exercise but it’s frustrating not to see this work reflected in the app! Thanks in advance for any support!

Moderator edit: updated subject for clarity

[EdsonFitbit]

Welcome to the Fitbit Community, @Steven76.

I'm sorry to hear about the difficulties you experienced with your Fitbit Charge 4. Thank you for the information provided.

In this case, I would recommend restarting your Tracker by following these instructions.

In addition, you can set up your Charge 4 as a replacement device:

1. Tap the Today tab , and tap your profile picture.
2. Tap Set Up a Device.
3. Choose your device and follow the on-screen instructions to continue.

Hope this helps.