Unable to view Xfinity video in Safari

At the end of the day, Safari has decided to make it very difficult to run Flash Player.  You may need to experiment with other available browser.  For a friction-free experience, Comcast ultimately needs to update their offering to eliminate the dependency on Flash Player.

Details on enabling Flash Player in various browsers can be found here:

https://helpx.adobe.com/flash-player.html

So I go to my Safari and go to preferences and go to website and its not there. I have to turn on the thing like the website told me but it's not there

Are you at the XFinity site when you do this?  Safari lists the sites currently loaded.  If you're not on the site that has the Flash content you want to view, Safari will not display the site.

I had this problem, but I had not fully installed the flash player.  If you search your Mac for FLASH you'll find a downloaded disk image for a flash player installer.  Double click that and install.  I know it feels like a second level of installation but it's how Adobe works

Enable Adobe Flash Player for Safari