I can't oathenticate on my new domain

I keep getting 

{"message":"Bad Request","errors":[{"resource":"Application","field":"redirect_uri","code":"invalid"}]}

When I use the following auth url:

https://www.strava.com/oauth/authorize?client_id=MYCLIENTID&redirect_uri=https://MYNEWDOMAIN/rule10/activities/strava_callback&scope=activity:read_all

This is the same URL I used a long time ago on MYOLD domain.

Any thoughts on why this should be.

David