Oddly, the original and ffmpeg versions play fine on firefox (win 7, 64b, version 67.0), but the krisp version doesn't respond when clicked. I don't understand

Oddly, the original and ffmpeg versions play fine on firefox (win 7, 64b, version 67.0), but the krisp version doesn't respond when clicked. I don't understand why not, as all samples are links to .wav files. It works on chrome.