The logo was previously working on this site as well. That was when it was using the standard site logo on mobile. The site logo rendered on mobile, but it was pushing down the hamburger menu to a second line and it looked weird. So I was advised by Support to upload a different logo for mobile. I uploaded a different size logo that would fit better in that small header, and now it is not visible at all. On my other site where the logo is working fine on mobile, I did not have to use a special logo on mobile and it just used the standard site logo.