Because of the recent bug report, PM add-on is updated now to the version 2.3.2.

Under customers area, purchasers are welcome to re-download the package and update addon_pmail.php file.

I've upgraded to this latest version and everything works fine but in the header where it says - Private Messages [0] aka {$pmView}

It doesn't change when I have a message? I am using mySQL mode without massmailing or reporting. I have went through the installation twice. It worked fine before. Any suggestions?

Everything I could tell you is that recent upgrade doesn't affect {$pmView} or any other code formed under bb_plugins.php. As you may check on minibb test page, it all works fine as previously, so maybe the bug is somewhere on your end, I don't have an idea where exactly...