Why is my Favicon not showing?

Hi - I guess this isn't strictly Wordpress related, but it is a frustrating problem nonetheless that other Wordpress developers must experience from time to time.

I have 3 sites that I'm working on. In the Apache http settings each redirects to https. With 2 sites, I uploaded the favicon.ico to the root folder and each worked flawlessly. I uploaded the same favicon.ico file to koobimo.media and no matter what I do it still displays the Plesk Favicon.

I have:

Manually deleted and replaced the favicon files
Refreshed my cache and deleted history countless times
Rebooted the server

When I manually point my browser at the file (https://koobimo.media/favicon.ico) I still get the Plesk Favicon even though I can clearly see the correct one sitting in my ftp programme!

any idea?