Favicon for a subsite not displaying on Chrome

Good morning. We have a separate favicon used on one of our subsites that used to display correctly, but due to a recent update of Ultimate Branding the favicon on this subsite is now the "blank paper" icon in Chrome. Strangely enough, the favicon selected for this subsite displays correctly on its Dashboard, just not the live front-end.

The favicon that we're using is a 512X512 PNG.

We have the favicon set through Appearance / Customize.

We have also removed the favicon from Appearance / Customize, and gone to Branding / Images and tried to set it there. Every time you leave the Branding / Images page though the icon reverts back to the Main site Favicon.

We leave the checkbox for "Allow favicon defined here to override the site icon defined in Appearance > Customization" unchecked, of course.

Any ideas as to how to correct this issue? Thank you.