It does work fine for me, so what the hell.
Do you get any error messages?
Nope i don't get any errors. Il make a video of it tomarow

ok i created a video. but it is again a bug with Firefox as i show in my video:
Oh I thought you were talking about in-game chat. I'll look into this
nope it still doesn't work for me

omg so weird if i use the webchat and i look in-game i see that, but firefox doesn't show any chat.
It works for me in Firefox.
Also it was not a bug in the Core plugin but in MCServer itself, so you need a new .exe
It should work. Restart your browser and try again. If problem persists press ctrl + shift + j and look for errors (to be sure refresh the page with this window on). If there is something, paste it here

it only works with firefox when i refresh the page manualy.