Since this is an Appronto module you could try to reach them on the mail that is provided on the page of this module in the appstore (Info@appronto.nl).
Regards,
Ronald
What I can see is that the Chatter widget (Code is on Github) uses an old setup for widgets and deprecations that will not work in MX6 (for example, mx.processor).
Like Ronald says, contact Appronto, or maybe file an issue on their Github repository.