Shelly Plug S not loaded in HA

I have a couple of Shelly Plug S devices which I cannot load into HA. the plugs have an internal IP and can be seen in my LAN, but they are not discovered automatically in HA. Also a manual coupling does not work. according to several YouTube posts this should work fluently, so what am I doing wrong?

Have you installed the Shelly integration?
https://www.home-assistant.io/integrations/shelly

Problem is already solved, thank you for replying. MCast was not functioning