Why does Plex not work on my Vizio TV Model M60-C3?

I have a Vizio 65" 4K UHD Smart TV Model M60-C3. It comes pre-loaded with the Plex App. I just signed up for Plex services and installed on all my devices, 2 lap tops, desk top, tablet…all work fine. When I activated service on my Vizio, it never loads. All I get is the Plex Logo. This is the main device tat I want to watch my media on. Does anyone know why this is happenings