Hi
The following steps may help:
If you have not yet done so, update your iPhone and Apple Watch to the latest compatible software versions, starting with your iPhone:
- Update the iOS on your iPhone, iPad, or iPod touch - Apple Support
- Update your Apple Watch - Apple Support
Close certain apps and restart both your iPhone and your Apple Watch:
- Close the Watch app and Photos app (if open) on your iPhone:
- Double-click the Home button, then swipe up on each app preview to close the apps.
- Turn both devices off together, then restart your iPhone first:
Check that your Apple Watch and iPhone are connected via Bluetooth:
Check that you are following the instructions here to select and sync photos from your preferred album:
- It may help to change the selected album and then change to it back again.
- Choose your album and manage storage
If the issue persists, then it may help to unpair and re-pair your Apple Watch:
- The Watch app on your iPhone takes a backup of your watch automatically when unpairing via the app.
- Initially choose to Restore from Backup during set up (most data and settings will be restored, with some exceptions, such as Apple Pay cards, passcode).
- If the issue persists, consider instead unpairing and setting it up as a new watch.
- Unpair your Apple Watch and iPhone - Apple Support
- Set up your Apple Watch - Apple Support
If the issue then still persists, then I suggest that you contact Apple Support (remote diagnostics may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider for assistance: