Why does the app not allow me to import certain activities from a third party app?

It is up to the challenge organizer to decide which activities are enabled for your challenge. If an activity such as steps is not enabled, you will see them as “Unrecognized activity” and you will not be allowed to sync them.

Voor sommige challenges is het importeren van stappen of andere activiteiten niet mogelijk, omdat de challenge alleen bewuste workouts zoals wandelen of hardlopen stimuleert. Het importeren van dagelijkse stappen die ook alle stappen omvatten die je thuis zet, is daarom niet toegestaan.

You need to reach out to the challenge organizer to inquire if a new activity may be added as it is not in the discretion of teroGO to decide which activities are enabled for each challenge.