Well the title says it all!
However, to make it a bit clearer, this is what happens.
I have the plugin installed (automatically) on 000webhost.com.
When I add the shortcode like [cryptex]firstname.lastname@example.org[/cryptex] to a page, the result is that the page's content is blank. While the headers and other elements display as expected.
I also have another WordPress Site on eProhost.com that uses Cryptex successfully, but it uses a different theme. So, at the moment I suspect the problem is the Theme's incompatibility with the plugin... I have more inquiries to make before that can be established.
Hopefully, this will help.