AttendeesChat.js

...

class AttendeesChat extends Component {
    ...

    async componentDidUpdate(prevProps, prevState) {
        const { attendeesChatOpened, setUnreadCount } = this.props;
        const { channel } = this.state;

        if (!prevState.channel && channel) {
            this.init();
        }

        ...
    }
        
    async init() {
        const { channel } = this.state;
        await channel.watch();

        channel.on('message.new', this.handleNewMessage);
    }

    handleNewMessage = async () => {
        const { attendeesChatOpened, setUnreadCount } = this.props;
        const { channel } = this.state;
        const unread = await channel.countUnread();
        setUnreadCount(attendeesChatOpened ? 0 : unread);
    }

    ...
}

...