Appears that I have followed all of the steps and fixes that I've found both on this forum, as well as other places - to prevent unregistered users from posting on our PHPBB3 forum. I have edited permissions from every angle possible (that I know of), and still no luck.
The one thing that I've seen mentioned, but cannot locate in my moderation panel is an option for to dictate that only "Registered Users" can post new, or reply to threads. Perhaps that is the missing key? If so, where is it located?
If that is not the missing key, what else can I do to prevent outsiders from posting once passing the captcha feature? Not the one who set it up - this whole thing kinda fell in my lap. Thanks for the help.