[Theme Horse Support Team]

Hi Sam,

I think this issue is not just creating the child theme. If you just like to add CSS then you may use our custom css which is inside theme options. Child theme is mainly used for code customization. Once you deactivate all the plugins that you have installed in your dashboard. Because some of the plugins may conflict so that your menu is disappeared. If we find any issues regarding to this topic then we will let you know.

Thank you!