I created a Header Element to apply a different logo to a custom post type, than the rest of my site.
The logo I uploaded for the element is showing on my phone (above the GP menu control), and it made me realise that the other logo (i.e. the non-Element logo for the rest of the site) is not displayed for phone.
Why might this be, I have uploaded the normal and retina logo files for both the Element and the normal and retina logo files for the rest of the site under Customising > Site identity. But only the Element logo is displayed, on my CPT.
I notice a mixed content error in the console, this is because the Retina logo is being requested from HTTP instead of HTTPS. Remove the retina logo, clear caches etc to test if thats the issue. Then try and upload a new renamed retina logo and select that instead.