Thank you! I added the below to the wp-config.php file and I can successfully login on FireFox. Admittedly, I had not tried accessing via Firefox before reporting the error, so success in Firefox may/may not be related to the fixm though I'm still calling it progress.
In FireFox, I am able to still get to the WP-admin.php page, login and proceed to the admin panel.
However, in Chrome I see the following error:
You don't have permission to access /wp-admin.php on this server.
If I then access the external blog (without logging in) and go to the login link from the blog page, I am directed to wp-login.php (instead of wp-admin.php) and once agein get the cookie error once again
Of note/possibly related: For some reason, when I visit the site (main blog page, not the login/admin pages) using the domain name, I do arrive at the default blog page, however it resolves as the IP address, despite having the correct A record tied to the external IP, CNAME settings for www, etc., etc.
Thank you again for your help.