Hi
You may have configured your Apple Watch to use Wrist Detection and Unlock with iPhone. To unlock your watch, you need to wear it and then unlock your iPhone, which then also unlocks your watch. This can be configured differently.
First, check that your iPhone software is fully up to date: Update the iOS software on your iPhone, iPad, and iPod touch - Apple Support
Then, on your iPhone, in the Apple Watch app, go to:
- My Watch > General > Wrist Detection - check this is on (also try toggling it off, pausing for a minute and then toggling it back on again).
- My Watch > Passcode > Turn Passcode On, then set either a simply (4-digit) or longer passcode.
- My Watch > Passcode > Unlock with iPhone - also enable this (if it is not already).
Having made the changes, it may help to restart (or, if that doesn't help, force restart) both your iPhone and your Apple Watch.
- Restart iPhone: Press and hold the Sleep/Wake button until the red slider appears; Drag the slider to turn your iPhone off; When it has finished turning off, press and hold the Sleep/Wake button again until you see the Apple logo.
- Force restart iPhone: press and hold both the Sleep/Wake and Home button for at least 10 seconds, until you see the Apple logo.
- Restart Apple Watch: Press and hold the side button until you see the Power Off slider; Drag the slider to turn off completely; Afterwards, press and hold the side button until you see the Apple logo.
- Force restart Apple Watch: press and hold both the side button and Digital Crown for at least 10 seconds, until you see the Apple logo.
After putting it on your wrist, your watch should now unlock after whatever you do first: either unlock your watch with the passcode or unlock your iPhone.
Using a Passcode can also avoid other potential problems, such as:
- If you are without your iPhone, your watch may become locked after temporarily losing contact with your wrist.
- If your iPhone gets misplaced or stolen.
Enabling Wrist Detection and a Passcode is also required if you want to use Apple Pay on your watch.