First is the super admin member default is 2.
If you changed the id then possibly the new member was not a admin to begin with.
But I would think that registration would still work.
First thing i would do is look at /includes/config.inc.php
Check the first several lines.
change the MAIN_ADMIN_ID back to 2
And check if the other top lines for database connection,user and password are correct.
If the file is completely blank,that is your problem.
Just re upload a backup.
