Cannot access Amazon Prime on Comcast Xfinity

For a LONG time (1year) I've had difficulty connecting Amazon Prime TV through the Xfinity box. If I persist, I might make a connection after 15 or 20 minutes. After I get in, for some reason I have more diifficulty if I try watching a TV  show like "Yellowstone" where I have to pay for each season.  It''s easier connecting to a free show. 

Does anybody have an idea of how I can get this fixed or do I have to go to another cable provider?

Jimbo42