According to the release notes, this is a bug in the Atlas Response pages in 7.5.0. Upgrade to 7.5.1 to fix.
https://docs.mendix.com/releasenotes/desktop-modeler/7.5
"In 7.5.0, it was not possible to use the Generate page functionality for buttons in the Responsive profile. The Create Page dialog box showed no selectable page templates for this profile. We fixed this.