Hide element on mobile not working

Hi. I’ve got a theme called Kids Toys Store by WP Radiant and am working on a child theme from it. I want to hide my logo on mobile phones but the Otter Blocks visibility settings don’t seem to be working. Just nothing at all happens. I have checked on a mobile that’s not been used before to access the site, I’ve disabled all plugins and reactivated just Otter Blocks; I’ve tried it on 3 other themes; cleared caches on the site and browser – no change and I don’t know what else to do. Showing the logo on the header on a mobile makes a mess of it, so I do need to sort it. Any ideas please?

I’ve added a link to bypass the coming soon page – please excuse the mess in there!!

The page I need help with: [log in to see the link]