I would try calling Fitbit support. Basic trouble shooting have you tried deleting and reinstalling the app? That can fix the connection issues sometimes
Call the store and ask them specifically. Calling the Fit bit manufacturing company helps too.
Returns with a receipt in the first 30 days should not be a problem. Bring the original packaging. If you don't have it there may be a small charge. If you are exchanging it for another, offer the packaging from the second to avoid this charge.
I agree with Ariel and Dont'e.
I would just return it for a new one.
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