Error Code s3014

I seem to be having problems with every iteration of Plex besides iOs. When I try playing almost any file, I get a Error Code s3014. I’m not sure why some play and some don’t and I really don’t know why I can use my iPhone and iPad and have no difficulty at all. My Roku, my LG TV and my browsers will simply not play things. I thought maybe it was mkv but some do play. Any fixes? Any changes to my settings? Thanks in advance…