Hi
I suggest that you follow the instructions here, if necessary including unpairing and re-pairing your Apple Watch - including if either or both of your devices indicate that they are connected, but they do not behave accordingly:
- If your Apple Watch isn't connected or paired with your iPhone - Apple Support
- Unpair your Apple Watch and iPhone - Apple Support
- Set up your Apple Watch - Apple Support
If your Apple Watch is currently unpaired according to your iPhone, but not according to your Apple Watch, then you will need to erase your Apple Watch manually before being able to re-pair it:
On your Apple Watch: when viewing the time, go to the Home screen (via a single press of the Digital Crown) > Settings (gear icon) > General > Reset > Erase all Content and Settings > confirm when prompted.
Be sure to check that your new iPhone is updated to the latest version of iOS before re-pairing your Apple Watch to it: