Customize fails after server change

Hello,
i have changed the server of my blog and now it is impossible to customize my Sydney theme. Every time when i go to the customize link

http://wp.pestalozzi-gymnasium-heidenau.info/wp-admin/themes.php

i see this blank page:

http://wp.pestalozzi-gymnasium-heidenau.info/wp-admin/customize.php?return=%2Fwp-admin%2Fthemes.php%3Factivated%3Dtrue

If i try this with a standart theme it works perfectly. I have deleted the complete theme and the folder and installed new but the same problem.

Have anyone a solution for me?

Best regards, Patrick

Hello there,

I am sorry you have run into issue.

Could you please share the working login credentials to your site admin area, so I can take a closer look directly from there? For security reason, please send them privately to kharisblank@gmail.com and mention the link to this thread.

Regards,
Kharis