Dog eyes are very different from human eyes. Dogs' retinas only have about 20% of cones, which help us perceive color and detail. By comparison, the human retina has about 60% of cones. Therefore, dogs’ perception of color and detail is much worse than that of humans. In addition, dogs' eyes are adapted to fast-moving objects because early in their evolution, dogs needed to make decisions about how to hunt based on the movement of their prey.
However, in videos on electronic screens, objects often move faster than what dogs observe in the wild. Much slower, so the dog seems to have a hard time understanding the video on the electronic screen.