Hi Guys! If you have updated the information on your ArriveCan and you don't fly on the date you mentioned there you study permit gets invalid. It is not just because of the medical. In my case flight got cancelled and I had already updated the information on my ArriveCan that I am arriving in canada but as I was not able to fly and did not clear the immigration on that particular date so my visa was invalid. I called the High Commission of Canada and they told me that you need a new stamp otherwise the Border Authorities won't let you in. So I sent my Passport again, they cancelled the Previous stamp which was invalid and issued me a new welcome letter and also a new stamp. Only then I was able to fly. Please call the high commission in your respective countries to confirm that.