Why can't I type a message?

Put the summary of the bug you're having here

What I expected to happen was...:
I just type the message in sign

What actually happened was...:
The text on the sign disappears, and only a notification appears that the chat is also hidden from the server.

and, I was just alone for six hours in my friend's realm

Steps to Reproduce:
1. idknow
2. ...
3. ...