Audio within Course Presentations

Hello,

 

Please forgive me as I am not the most technical and feeling my way through this.

Using a Moodle, I have been creating course presentations. Howewver, I am having issues with the upload audio feature.

I have successfully managed this just the once, and the microphone button turns blue.

However, subsequently the microphone button turns green and no sound happens. I am using an Mp4 format, and the clips are around 30 seconds in length.