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A warm welcome to the Community @Roxy2013, thanks for troubleshooting this by yourself.
If your tracker isn't registering your heart rate information, I recommend taking a look at this post, where you will be able to see some things that might be affecting this reading and some tips to improve it. Also, I recommend verifying that this option is on or auto by swiping to settings and check your hear rate feature.
I hope this helps, let me know the outcome. 
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Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
Hey there @Wsmmom, welcome to the Forums!
I would like to know if you have take a look at my previous post? If you haven't, I recommend doing this and follow the instructions provided there.
Keep me posted! 
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