Issue on "Customize" page

Hello,

I have an issue when I go on Appearence -> Customize.
This is the only page I can see : https://tof.cx/images/2017/06/04/90dd725c7fde7c0e3cddbb35c5a876a6.jpg

Can you help me ?

(I just installed GreatMag in a new installation of WordPress 4.7.5 and the only plugin I have is Page Builder by SiteOrigin).

And this is the url of the issue :

MYWEBSITE.com/FINAL/wp-admin/customize.php?return=%2FFINAL%2Fwp-admin%2Ftheme-editor.php

Hello @zendium,

Please make sure that your server meets WordPress requirements. You can contact your hosting provider support regarding this. And here you can find those requirements:
https://wordpress.org/about/requirements/

Please feel free to ask any other questions that you might have.

Kind Regards, Roman.