Unfortunately, there was an update error on Samsung’s side however this has since been resolved. To relink, you will need to delete the app completely, download and reinstall it then relink your device.

Below is the step by step guide to doing so.
To enable the necessary permissions on your device, please follow the below instructions:

Go to Samsung Health and click on
More > Setting > Account > Samsung Account(Need to log in) > Auto sync On > click "Sync Now"
Go to data permission page > All data On.
Open FitVault and “sync” your activity.