Hi
How notifications behave depends on the status of your devices and your settings. With Wrist Detection enabled, in order to bring notifications to your attention as soon as possible:
- If your iPhone is unlocked, you will receive notifications on your iPhone instead of on your watch.
- If your iPhone is locked or asleep and your watch is unlocked (regardless of whether the watch screen is asleep or awake) and on your wrist, you will receive notifications on your watch.
- If your watch is locked or has Do Not Disturb enabled, notifications will go to your iPhone.
With Wrist Detection and passcode enabled, it may help to check that you are unlocking your Apple Watch after placing it on your wrist and that you are wearing your band sufficiently snugly.
Your Apple Watch may otherwise lose contact with your skin, causing it to be believe that it has been removed from your wrist. Wrist Detection can also be affected by temporary or permanent skin changes, such as by some wrist tattoos.
More information:
Notifications on your Apple Watch - Apple Support