[Theme: Customize] Problems with Favicon

Hello, well, I made a Theme and it’s working fine. The problem is that the wp is in one directory and the url of the site is another, is a subdomain in my site. If I get in the WP dashboard, the favicon appears, because there I go like: https://www.myurl.com/sitename/wp-admin, but in the site, that is: https://sitename.myurl.com they don’t show.
I tryed some codes that the people put here for problems with favicon, put the favicon image in the main folder, in the theme folder, and all locations possibles and change them in the code but didn’t work.
Someone can help me? Thank you!