Hello @Fh25 and welcome to the Community. Do you use an Android phone? Other Android users are reporting the same issue. My iOS app works normally. Fitbit seems to be aware of the issue, but there is no time frame for a fix. Nevertheless, Fitbit's Irregular Rhythm Notification Help article recommends contacting your doctor if you receive a notification.
Laurie | Maryland
Sense 2, Luxe, Aria 2 | iOS | Mac OS
Take a look at the Fitbit help site for further assistance and information.