Having trouble pairing watch with new restored iPhone

On a computer, go to iCloud.com and sign in with your Apple ID.

Go to Find Iphone.

Select All Devices, then click your Apple Watch.

Click Erase Apple Watch.

Select Next until the device is erased.

Click the remove button next to your Apple Watch.

Then try pairing the watch again.

Did you unpair the watch before you restored the phone?,if not the watch thinks it's paired to the phone and the hone doesn't.