Note: If you get Internal Server Error please see this guide
If your WordPress page is suddenly just white or you get a 500 error message, it may be good to enable display of error message on the page.
That is done through your wp-config.php file.
In that file there’s a row that contains:
That has to be changed to:
To reach and modify this file, you must log in to its FTP account via Loopia.
See here how to connect via FTP
Make the change on the line and re-upload the file.
You are most likely to receive an on-screen error message that may lead to an add-on (plugin) or theme. You can then, via FTP, update this plugin (search for this on wordpress.org download, unpack and then replace the files in your TP under folder wp-content/plugins /)
Then test if the page is working again. If it does not, delete plugins from the files completely from FTP.
When done, change to define (‘WP_DEBUG’, false); again.