When I tried testing it in the widgets page with no active livestream (no zapping, just pressing the "test" button), it makes the sound on that same webpage, but nothing shows up on the link provided by the widget, no sound or image alert, just a black screen.

Then I tried going live with the widget set up, and zapped myself the minimum ammount for text to speech with a message attached. I can see the message in my wallet (Alby) but the text to speech and image alert doesn't show up on the livestream, nor at the linked webpage the widget provides.

I'm sorry, I don't get what you mean by zapping from Amethyst or nostrudel.ninja, I'm zapping directly from zap.stream with Alby.