Latest questions about "device error"

The light on my Fitbit won't turn off after I did a firmware update on it. Can someone please help me, I don't want to buy a new one of these?

It worked well for a long time, but recently I've received a message saying that I have to plug in a supported device. Does anyone know how to solve this problem?

When trying to add Counter or Device Status Notification I get the following error: The operations cannot continue due to an error in the application.