Just find out those two things on internet, I don’t remember where… With the plugin called “WP-Crontol” you can see the on-going tasks on your WP-Cron. Look if “nxs_querypost_event” is there or not. If it’s not, try toc reate it: just put that name and that’s all you need to create it. No code.
If it gives problems to you (like you can’t create it or you can’t adjust a 60 seconds interval) try to do it changing your theme to one of the defaults from WordPress.