Please check your tour information again because user only can cancel before number day before the arrival.
For example: user book tour today (8/9/2017), your setting for tour cancelation is 7 days before the arrival. If you book this tour in 10/9/2017 (2 day later), you can not cancel. But if you book tour in 16/9/2017 (over 7 days), you can cancel your order.
Please check again.