Blank pages can be seen in wordpress if the X-Frame-Options are set to deny. You can view the problem using browser dev tools and view the console log.
X-Frame-Options are used to indicate whether or not a browser should be allowed to render a page in a frame, iframe or object. Sites can use this to avoid clickjacking attacks.
Changing from DENY to SAMEORIGIN should work in most cases.
add_header X-Frame-Options SAMEORIGIN;