The messages are probably showing up under "Inquiries", so you need to switch over to that tab on the "Messages" page to see them. BTW, we're currently pulling in all NIP-04 DMs, so messages aren't all listing-specific; that will be changed in an upcoming release.

Usernames are also already displayed, they might just not appear due to network issues or latency. Refreshing usually fixes that. 

 And if you can't see the "Orders" and "Inquiries" tabs up top on the "Messages" page it might be due to the window size; will push a fix if that's the case.