The Fitbit needs to be restarted

Despite its size, your Fitbit is still a computer. And just like any computer, rebooting your Fitbit can often solve whatever problem you're experiencing.

If your Fitbit still has some battery life left but simply won't start charging, it might have a software glitch and needs to be restarted.

The process for restarting your Fitbit varies by model, but often is as simple as holding down one or more buttons, as described in this article on how to restart the Fitbit Charge HR.