Fitbit Product Experts Alumni are retired members of the Fitbit Product Expert Program. Learn more
I'm not sure that fitbit are addressing a problem so it's probably best to try some troubleshooting on your device in the hope of getting it working again.
Assuming it's the Alta HR that you have, try restarting your phone and then restarting your fitbit using this procedure:
Give this a few tries as it doesn't always work. If it still won't sync after that then there are some more ideas to try in this help file: http://help.fitbit.com/articles/en_US/Help_article/1866
Fitbit Product Experts Alumni are retired members of the Fitbit Product Expert Program. Learn more
Sorry, but you only said you had the "HR". Rather than guess again, here's the help file that has the restart instructions for all trackers.