Why is the loaded font not being displayed via @font-face?

Question

Fonts

Good day! Checkout question.
The custom font is not displayed on the site, loaded via @font-face. How to solve the issue?
On the personal computer on which I work, it loads, because I have this font in my database. On other devices, including mobile (!), It is not displayed in any way. Generated through a generator, registered in folder 755, checked for downloading the font via a direct link - it works. But it doesn't work visually.
Tell me please.
Here is my code:

@font-face {
  font-family: 'FuturaPT-Demi';
  src: url('FuturaPT-Demi.eot');
     src: local('☺'), 
     url('FuturaPT-Demi.eot?#iefix') format('embedded-opentype'),
    url('FuturaPT-Demi.woff2') format('woff2'),
    url('FuturaPT-Demi.woff') format('woff'),
    url('FuturaPT-Demi.ttf') format('truetype'),
    url('FuturaPT-Demi.svg') format('svg'),
    font-weight: normal;
    font-style: normal;
}

h1, h2, h3, h4, h5 { 
    font-family: 'FuturaPT-Demi', sans-serif;!important 
    }

Answer 1

Most likely your fonts are in a folder, and the paths are written to the root (in the same place as the styles). They work on the computer because these fonts are probably installed in the system.