User browser/security settings most likely.
In my experience anyway

Doesn't mean there is anything wrong with your link or your site, just some rule on their system.

Like how Outlook defaults to not downloading images without you telling it to.
'Right click to download images' ...
.. and GMail actually downloads a copy of the image to its own system, then decides whether to display it or not.

lots of security stuff these days and growing exponentially.
Hard to keep on top of it sometimes

I mean, I suppose it could even be a simple CORS issue

https://www.google.com/search?client=firefox-b-1-d&q=browser+CORS+issue
Link is a Google search for CORS in case this is new to you

Coming to a Browser near you (soon) if it hasn't already

I do not work here, but the benefits are still awesome
Make your sound your own!