Play formats with large files

I have some large 4k files, some ISO’s, and some m2ts. When I try to play the m2ts I get the playback error: This client isn’t compatible with the media and the server isn’t sending a compatible media format. With iso’s I have the iso mount plugging installed, but the file looks like it will play but just spins as if it’s trying in the backend. I let it load for a while just in case it’s taking the time due to it being a large file