Website Logo Not Resizing on Mobile

I used to use the 3.0 version of Orizon which featured the websites main logo automatically resizing on mobile devices.

After upgrading to the 4.0 version of the theme this no longer works.

I can play around with the CSS so that the image DOES resize according to the % size of the container, which fixes the size for mobile, but then blows the size up too large with a regular window size. 

Any help would be greatly appreciated

Mike. .