Full Board URL: https://www.nostalgiadragracers.com/forum/
XMB Version: 1.9.12

I have https://www.nostalgiadragracers.com/forum/ set as the URL in the settings - but if I enter www.nostalgiadragracers.com/forum/ I get the unsecure HTTP version

If I go with the secure of https://www.nostalgiadragracers.com/forum/ version - but if I click the admin link it goes to unsecure HTTP


What am I missing?

That is odd.

When you mention settings, can you check
config.php
which has a variable setting $full_url which should be set to
$full_url = 'https://www.nostalgiadragracers.com/forum/';

then

https://www.nostalgiadragracers.com/forum/cp.php?action=sett...
Full Site URL: should normally be set to
https://www.nostalgiadragracers.com/ but I suppose
https://www.nostalgiadragracers.com/forum/ would be ok

If something mentioned above fixes it and it works correctly, I'd suggest redirecting all web traffic to the secure site:

Open .htaccess if it exists in the root directory [take a backup of it first], or create it if it doesn't.

Find the line RewriteEngine On if it exists and insert the last two following lines of code below it or all three lines if it doesn't exist.

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

Let us know how it goes.