Same problem here. Tried the "revoke access" and then reconnecting thing several times, but that didn't work. Reached out to the people at Strava, but they tell me it's a Fitbit issue. Please fix this, cause it's indeed really frustrating. It has been syncing slower the last couple of weeks for me btw. Thought I should mention. Been doing the manual sync now by uploading txc file to Strava, but hopefully the automatic sync will work again soon. Thanks!
