I spent several hours on the phone with Fitbit and got no solution from them. Horrible customer service. Anyway, I eventually realized that it was because I put my contacts in fancy fonts, so I had to go through my contacts and remove the fonts and emojis. So if you have emojis and/or fonts in your contacts then removing them should help.
After doing this, the problem happened again. This sequence worked.
1. Go into your Bluetooth settings and forget your Fitbit. Also delete it from the Fitbit app.
2. Plug the Fitbit in and click the button on the charger three times until it powers off.
3. Power down your phone.
4. Turn the phone back on and go into the Fitbit app and setup your Fitbit again.
This worked for me, but you need to do it in this sequence for it to work.
