I will be investigating this again.
However - Please remember that registered visitors can Turn Off Private Conversations in their Privacy Preferences:
https://elsmar.com/elsmarqualityforum/account/privacy
The Default Setting when someone registers is "Members" but it can be changed. I mention this because you may be wanting to start a Private Conversation with someone who has it turned off.
As a test, you can always try to start a Private Conversation with me. If you see a link and you have posted at least 5 posts you should see a link to "Start a Private Conversation" when you mouse-over my avatar.
I also want to remind everyone that the reason for limitations on Private Messaging for people with less that 5 (I'll double chack but I think I reduced it from 10 posts, is that in the past vBulletin days we found some people would register but never post, with the intent to send people SPAM messages. We found out when occasionally someone would use the Report link to report the spam.