Look towards the end of your wp-config.php file, you should have the definition for ABSPATH looking something like:
/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
define('ABSPATH', dirname(__FILE__) . "https://wordpress.stackexchange.com/");
If it’s a static path instead of the code above, then this might not correspond to your current path. Either change this to the code above or read on and try the other way to fix the issue:
To see exactly where your files are currently located in the new installation, place the following line right at the start of index.php, after the opening php tag:
<?php
die(dirname(__FILE__) . "https://wordpress.stackexchange.com/");
Now when you refresh the page, you should see the path and according to the error messages in your original post, it should be /public/sites/www.glasloodje.nl – if that’s not the case, debug this or change the ABSPATH definition to:
/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
define('ABSPATH', '/absolute/path/that/shows/up/in/the/index.php/debug/message/');