Custom font being over ridden on one page

ELVIN,
If you’re already using a child theme, you can use the functions.php file to add your PHP.
I tried this ^ with the PHP for the site logo PHP Tom provided. NO LOGO.

I also tried adding the logo switcher code to Code Snippets and got a syntax error.

I added the php filter provided to recover GP HOOKS in GP and it is still not present.

I've tried deactivating ALL the plugins and adding them back one at a time. None of the plugins appear to be interfering in the appearance/disappearance of the logo.

Still haven't addressed the issue of the font which was the only issue I had when we started ;)

I'm confused why I'm having so much difficulty getting your apparently simple instructions to work?
I am also getting frustrated that the proposed solutions don't appear to be working.

What is the next step here?

Quick question - do you have backups of the site ? As it may be easier to roll back to a version before those changes 'broke' your logos. Then we can revisit the issue of the font. Let me know.