How to set up an Ionic after a factory reset?

[SunsetRunner]

after resetting factory settings the fitbit ionic no longer displays anything except the logo. when I restart it, a message in several languages tells me to go to www.fitbit.com/setup to get started.
After that, I don't know what to do.
Thank you for your help
Lelièvrerouge

Moderator Edit: Clarified subject

[CindyMFitbit]

@SunsetRunner It's nice to have you on board!

Thanks for the details shared on your post. After the factory reset you need to set up your Fitbit Ionic as new device using the Fitbit app, so please do the following: 

1. Open the Fitbit app, tap the Today tab and tap your profile picture
2. Tap Set Up a Device.
3. Choose your device and follow the on-screen instructions to continue.
4. If you are having trouble to set up the device again, please see Why can't I set up my Fitbit device?

Hope this helps.