infoway child theme blank screen

I cannot create a child theme for the InfoWay theme

I have done everything right:

I have a folder called /httpdocs/blog/wp-content/themes/helptwentyfive

in that folder I have screenshot.png, and style.css containing:

/*
    Theme Name: helptwentyfive
    Description: customised InfoWay child theme for helptwentyfive
    Template: infoway
    */

    @import url("../infoway/style.css");

In Manage themes, at available themes I have the helptwentyfive theme with screenshot, all ok, but when I click preview theme, or install theme I have a blank screen