just copy the video URL and paste it in a new tab. It is because of the new URL shortening that youtube does if you grab a link using the youtube "share" button. You will notice if you copy the URL and paste it into a new tab that the URL will start as a short URL from the "youtu.be" domain e.g. https://youtu.be/3ew6FWBol4I and then will resolve itself into the proper youtube URL (which should play fine for you) e.g. https://www.youtube.com/watch?v=3ew6FWBol4I
I just wanted to note that as you see it all the time and 99% of the time if the video is showing as unavailable it is because of the reason outlined above and all you have to do to watch it is open the URL in a new tab.