Apple TV HD buffering
I have just bought new iMac retina 5K 27inch 2019,3ghz 6 core intel core i5, 16gb ram, os catalina 10.15.6 and a new apple tv hd and now have severe buffering problem, movies stop and start and the time line stays on the bottom of the tv screen with spinning wheel next to time which doesn't change even if movie is playing. Question is have I done something wrong with setup (I have gone through out all again and checked for updates) or just coincidence and I have a network problem and maybe need a new modem?
Apple TV HD, 13