[Plugin: Static Random Posts Widget] Refresh doesn't work

Widget shows a list of posts correctly but it never refreshes and when I click the refresh button it goes to a blank page with this as the url:

https://www.mywebsitenamehere.com/wp-admin/admin-ajax.php?action=refreshstatic&number=3&name=widget_staticrandomposts&_wpnonce=f36f07c411