Custom Theme Not working for some people

I designed this them for someone and it worked for me on my server look here THEME INSTALLED. I then tested it on the newest version 2.2 and it worked there also. I sent them the them this ZIP FILE containing the them and they said it wouldn’t work. Then they told me that had an older version of WP so I asked them to upgrade they said they did so but it still shows a blank page instead of loading the theme but all other themes work just not the one I designed. Can someone tell me what they think see if they have the same problem. Look here you can see there install but the screen stays blank https://vonniederhausern.org/testblog/