Cannot reply to messages

Was trying this plugin out on my BBPress forum but it does not work ??

I can send an initial message to a user, but after that they cannot reply. I type my reply to the user, click send, and nothing happens, no reply is created, no notification, nothing.

e-mail notifications are kinda broken too, with garbled HTML, they say e.g:-

<p>Dear BuckoA51,<br />

The page I need help with: [log in to see the link]