Hello @fmaerevoet
Are your activities GPS based? For some reasons Fitbit, and only Fitbit, decided that the only activities worthy to be sent to Strava are only does tracked with GPS.
The Fitbit Sense 2 is a GPS tracking device
Best Answer@fmaerevoet, not every activity will use GPS and you can turn on/off the GPS. The thing is, if you track activities like Workout or Spin none of these will be synced with Strava because they don't use GPS. If you run/walk with GPS this should be synced. If you do the same without GPS (GPS is off) then it won't be synced.