Would you help to understand why my font change according to the browser?

I'm using the following code:
@font-face{

font-family: 'San-Serif';

src: url('https://bolsadevalores.yul1.qualtrics.com/WRQualtricsControlPanel/File.php?F=F_jmc99Dhkab4lWdy');

}

h1, h2, h3, h4, h5, h6, p, div, span, a {

font-family: 'San-Serif';

}

When I try it in the Qualtrics preview It's all right, but when I send the survey, the font change. It is applicable only in Safari.