Hi
Check that Bluetooth and Wi-Fi are both enabled on your iPhone:
- Phone: Settings > Bluetooth - on.
- Phone: Settings > Wi-Fi - on.
Check that your Apple Watch and iPhone are connected:
- When viewing the time on your watch, swipe up on your watch face > swipe left / right to the Settings Glance > check that this states Connected and shows a green phone icon.
- Disable Airplane Mode if it is enabled.
It may then help to restart both your iPhone and your watch. Turn both devices off together first, then restart your iPhone before restarting your watch:
- To turn your watch off: press and hold the side button until you see the Power Off slider; drag it to turn off;
- To turn it on: press and hold the side button until you see the Apple logo.
Otherwise, it may help to unpair and re-pair your watch. The Watch app on your iPhone takes watch backups automatically, including a fresh one when unpairing via the app. Choose to restore the watch (Restore from Backup) when offered the option during set up. Most data and settings will be restored, with some exceptions (eg Apple Pay cards, passcode).