Strava is not working on new Apple Watch 6

I have just purchased apple watch 6 having had an apple watch 1. All apps have uploaded and working again apart from Strava. Even though I have Strava on my iphone and have an account and have set up to connect to Apple Watch in the Strava app on iphone, I get the following on the Apple Watch Strava app when I open it:

"On your phone, log in or sign up using the Strava app"

I have tried deleting the app on both phone and watch, logging out, logging in but cannot get the Strava app on phone to work even though it worked in the past on old phone.

Very frustrating as this is the app i use more than any other.

What do I do?