聊天功能无法使用,是需要订阅以后才能使用么?

聊天界面的邀请是无法使用的

Invitations via the chat interface are unavailable.

Do you mean your not receiving “email calendar event invitations” in the chat window ?

Or

Do you mean your not receiving “chat request invitations” from other chat apps, and if so what specific chat app is the sender using ?

Can you elaborate on that.