Are you getting the above error message as well?
After doing a fresh install and enabling multi-sites I couldn’t see the Domain Mapping and Domains sub-menu options under Network Admin / Settings.
I loaded up my trusty editor and confirmed
define('SUNRISE', 'on' );
was in fact in the file. It was slightly higher than where it said, it’s not important, but I moved it anyway, and I still got the error.
I checked and sunrise.php was in fact in the correct location under /home/public_html/wp-content/sunrise.php
So how did I fix it?
The problem was, it was the incorrect (read:old??) sunrise.php file!
Copy the correct one from:
/home/public_html/wp-content/plugins/wordpress-mu-domain-mapping/sunrise.php
and replace the previous one, and reload your admin page. You will now see the welcoming domains page :D
If you want to find out more as to why it happened, and how it is that my sunrise.php got “moved” or “re-moved”, it was due to a conflict by domain mapping plugins. I’ll be blogged about it in the near future and it will appear here (currently in draft and not published).