The group still doesn't appear in Group Admin, but here's my progress in troubleshooting. Any guidance/adivce would be greatly appreciated.
The Group Admin display does in fact have a row for the Logged-in Users Group, which I've determined elsewhere should be group id 13, but it's a very short, blank row, only a few pixels tall. I didn't even notice it until I viewed page source, which revealed empty data fields for that group, but by reading the data from the other groups I can see what's missing. Now, the questions in my mind are "what supplies the data to this .php page, and why isn't it working as expected?"
If I manually enter the url
http://www.pogowasright.org/admin/group.php?mode=edit&grp_id=13
I get the error message "To edit this group, you have to be a member of the group. Please contact the system administrator if you feel this is an error."
Also, I've determined that there's no listing for Logged-in Users on Admins Only / Users / Security Groups, so I can't ensure users are flagged as members of the group.
This is all very informative, but I haven't yet figured it out. Could it be that the group exists but is malfunctioning, that it needs at least one member before it'll appear? I realize if I'm logged in I should be a member automatically, maybe that's where the error lies...???
I'm hoping to clear this up soon, and am appreciative for any/all suggestions.