There have been many times when I had to fix a webpage (.htm/.html) where an image, sound file, or layout was wrong. In nearly every instance, it was because the code was missing something as simple as a bracket, quotation marks, or other special punctuation was missing.
Many times, a missing image was because the "source" (src) was either pointing to the wrong folder or the image was not in the correct folder.
Always put your sounds/music in a folder with the presentation, THEN TEST IT on another system! (This is why thumd/USB drives are so handy!)