Hi
If Nightstand Mode is not operating as expected, then it may help to follow these steps:
On your iPhone, in the Watch app, go to: My Watch (tab) > Passcode > check that Wrist Detection is turned on.
With your iPhone and Apple Watch connected via Bluetooth, check that Nightstand Mode has been enabled:
If the mode has already been enabled, then turn it off, pause for a few moments and then re-enable it.
Restart (normally) both your iPhone and your Apple Watch, turning both off together, then restarting your iPhone first:
When placing your Apple Watch into Bedside / Nightstand Mode:
- Check that your Apple Watch is standing on its side in a fully upright position (at 90 degrees to the surface), with the buttons on top.
- If you are using a third-party accessory such as a charging stand, then it may help to remove your Apple Watch from it and to instead place your Apple Watch directly on the table.
- Check that your Apple Watch is connected to the charger, correctly aligned and touching it fully, and connected to power.
- Check that you are following Apple's instructions for charging your Apple Watch, including:
- Using original Apple or MFi-certified charging accessories.
- If you are already doing so, try using another such cable and/or power adapter.
- Checking that all wrapping has been removed from all items, including checking carefully on the head of the charging cable.
- Checking that the charging cable and power adapter are fully inserted into the port and power socket.
- Check that you are placing your Apple Watch on a surface that is still and free from vibrations, whether from something that it is standing on or from something nearby (such as fan).
- Check your battery and charge your Apple Watch - Apple Support
- If your Apple Watch won't charge or it won't turn on - Apple Support
If the issue persists, then I suggest that you contact Apple Support (remote diagnostics and/or mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider for assistance:
More information:
Use Nightstand mode on your Apple Watch - Apple Support