If data such as settings, apps, music, photos, workout data, and health metrics fail to sync over Bluetooth/WiFi connection between Apple Watch and iPhone, follow these tips
Ensure that both devices have Bluetooth and WiFi enabled and within close proximity
Manually disable Airplane mode from both devices if they are already connected
Disable Low Power Mode on your iPhone.
Connect your Apple Watch to its charger as certain syncing features require it
Restart your devices and try again
Reset the sync data on your Apple Watch by going to the Watch app on your iPhone and navigate to General > Reset > Reset Sync Data.
Make sure that both your iPhone and Apple Watch are running on the latest version of their respective operating systems.
If the above solutions didn't work, unpair and then re-pair your Apple Watch. Lastly, make an appointment with an Apple Store if the syncing issue persists.