Fitness won't sync to Apple Watch 9 Series

When I try to start a workout on Fitness+ the app on my iPhone 15 pro max attempts to connect to my series 9 apple watch but eventually says it can't connect.

I have restarted both phone and watch

I have turned Bluetooth off and on again

I have turned airplane mode on and off again

I have turned wifi off and on again

[Re-Titled by Moderator]