For the longest time I had a problem syncing my ChargeHR to my iphone. Whenever I had to recharge and reset time, it would take forever to sync or wouldn't sync at all. I tried all the suggestions from Fitbit and community, some worked at times but were inconvenient (restart phone, etc.).
I finally found a solution. If I turn off the auto-lock feature on my phone, I am able to sync the Charge. Apparently the sync process was taking longer than the time set to auto-lock the phone and this was disrupting the sync process (I assume).
Go to Settings->General->Auto-Lock. Set to "Never". Sync from Phone app. Reset Auto-Lock to original setting.
Has worked every time. A little bit of a hassle but easier than other recommended solutions from Fitbit.
