Messages and Adding Contributors

Greetings everyone! I've been trying to make more of an effort to network with other creators on NotePD, but I seem to be having issues. I can't seem to select users to send private messages to or add users as contributors to posts I'm creating. So while I want to message this problem to @paolo directly, I seem unable to at the moment.

Has anyone else had this problem? I'm working from the desktop version of Firefox, so I don't know if this is an issue only for me, or if other users also had this problem. Any feedback is appreciated!

Edit: I figured out how to select users to send private messages to, but I'm still having issue with adding users as contributors.