You answer:

Hello. Yes, I confirm, I had similar problems with playing MP4 on Mac. I decided that the problem was not in the laptop but in the player itself. Therefore, I started looking for players that specialize in playing MP4 on Mac. I was advised to use reviews from experienced people in this field. Thus I found a list of the best source link players that solve my question. I recommend you to read it. It will definitely help you decide on a good player that plays MP4 on Mac. By the way, I chose Elmedia Player, and I like its work. It's like I've always used it, very convenient.