ClassicCar

I'm afraid that I have very little idea of how the system works (even though I'm a "moderator") because nowhere is it explained. Is it possible that the recipients of your PM simply don't know how to retrieve a message sent to them? Or are they telling you point-blank that they have opened their mailbox and find nothing from you in it?

Here's how one finds one's messages:

When one is logged in -- that is, when one's "avatar" photo appears towards the upper left of the page along with the words "Welcome, Dennis Dingleberry" (or whatever) next to them -- the words "Private Messages" should appear to the right of this, along with a list of four options (new messages, friend requests, groups invites, and events invitations). Clicking on any of these will open the corresponding list (assuming, of course, one has received one of these messages).