Ensure that the watch is connected to the phone using the NoiseFit app. Open the NoiseFit app and swipe down on the Homepage screen to sync data. If the issue persists, restart the watch and try again.

Takes a long time to sync the activity data to my phone

Activity data is usually very large, and therefore takes longer to sync. So Swipe down from the Homepage screen and wait for the watch to be synced. The Syncing is displayed on the top in Percentage value.