Thanks, Acorn. I've figured out what the problem is, but not got a solution yet. When I look at the site with Developer Tools in Google Chrome, I see an error that says:

Access to font at https://my-font-address from origin https://feed.surfing-waves.com has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin https://feed.surfing-waves.com is therefore not allows access.
I don't suppose you've got any ideas how I grant access, have you?!