I can’t get my apple I watch to sync to my new iPhone 13

From a web browser,sign in to iCloud.com with your Apple ID.

Go to Find iPhone.

Click All Devices at the top of the screen.

Click your Apple Watch.

Click Erase [device]. Select Next until the device is erased.

Click Remove from Account.

Then;

Setup your Watch to a new iPhone

Is it paired to this new phone? Did you remove it from the old iPhone? If you go to the Watch app, does it show that iPhone 13 as paired? If you look at the Watch, go to Control Center, do you see the phone icon in the top center?