Ok. Details why you see it how you see :
In our code, we are checking if it is mobile when the page starts to load
according to your video you just resized window from desktop to mobile view and that’s the reason why you see sidebar below, but if you refresh page with mobile view or check on real device you will see off-canvas as you want to
http://prntscr.com/218o1ah
Please, check as we recommend you above.
Regards