Oregon 700 won't sync with Strava while my Vivoactive 4 will synch with Strava

Hi, I'm puzzled. I record my activities on both my Oregon 700 and on my Vivoactive 4. Same ride; Vivoactive syncs nicely, Oregon doesn't. Both activities are shown in Garmin Connect. As the Vivoactive is syncing I assume the connection between Garmin Connect and Strava is correct and operational. What could be the reason the Oregon data synced to Garmin Connect is not picked up automatically by Strava?