Custom Code Not Showing on Mobile Devices

I have custom code added to my website www.bloom2wellness.com and it appears in the desktop version but not on a mobile device.  Ideas or suggestions on how to fix this? It is for an additional script font that appears throughout my site.  I'm at a loss on how to fix this and I feel it makes the site appear better. This is the code that I used. Thank you!

h3 {
  
    font-family: BRITTANY;

  font-weight: 500;
  
  line-height: .5em;
  
  font-style: REGULAR;
  
  text-transform: None;
  
  letter-spacing: .0em;

BRITTANY is custom font or Squarespace font?

If custom font, have you declared font-face yet?

@font-face {
	font-family: BRITTANY;
	src: url(paste brittany font file url here);
}

This isn't a Squarespace font, I downloaded the BRITTANY FONT and added it to custom files within squarespace.  Do I copy and paste the above and have it go to my C drive or custom files within squarespace?

Thank you! 

You can upload font from your PC to Squarespace, then add font file url here