Reply To: 404 page not found

The solution I suggested earlier doesn’t work. WordPress needs the register_post_type() calls in the init hook.
I’ve found the actual problem though, more or less.
You use the keyword ‘room’ throughout your code, in form field names, and $_GET and $_POST variables. I also use it as a post type name. WordPress confuses the two for some reason, and the plugin stops working.
Either the theme or the plugin needs a rewrite (probably both) so that they don’t interfere with each other or with any other theme or plugin.

A simple:

function my_rpt()
{
register_post_type('room');
}
add_action('init', 'my_rpt');

in any theme’s functions.php should replicate the problem for you to test.