I’ve read lots on the Fitbit not working with the iPhone X but nothing has been done about getting it sorted. I’ve ‘forgotten device’ on my old phone and tried to sync it up with my Fitbit, deleted the app and reinstalled the app a few times and it’s still not working.
I’ve had my Fitbit ionic for while and I want to send it back as the main reason for using it is to get Vitality points. I’ve ended up re-syncing my Fitbit to my old phone (which I want to sell but I’ve left it so my Fitbit app gets updated for Vitality points). Its been months since the iPhone X was released and I’m done waiting, I want to switch to a device which works so I want a refund on my Fitbit ionic but there’s no way I can return it because I don’t have the packaging. Fitbit needs to refund their customers for the poor service and put on the website clearly Fitbit devices won’t work on the iPhone X
According to the compatible devices page it should work.
Have you updated your phone to the latest IOS? Needs 11 or later. Apples power saving system can often lead to sync issues with 3rd party devices, that's about all I can suggest at the moment sorry if it doesn't help, happy if it does