Usage of Media Content on MyCloudEX2 Ultra

I’m now using a new MyCloudEX2 Ultra to store files downloading from in the format H.264 SD to look it afterwards on my TV. Unfortunately I’m informed that the format is not suported. Formerly I was using a MyBook and it was working without problems.
Do someone know what should be the problem? Why myBook is working while MyCloudEX2 Ultra is not? Should I check someting within the installation?
I’ve checked if I can stream the same format on an computer and it’s working. Does that mean that the problem isn’t the MyCloud but the TV? TV is brand new, that’s why I don’t know.
Many thanks,

@olferti You should place your question in this sub-forum.