FAQlinuxBlank - psiinon/zaproxy GitHub Wiki
Why am I getting blank ZAP windows on Linux?
Java has problems with 'non standard' window managers.
If you have changed from one of the main window managers and are seeing blank windows when you use ZAP then see http://awesome.naquadah.org/wiki/Problems_with_Java#Impersonate_Another_Window_Manager for potential solutions.