I am not sure where the broken link is.
I grabbed this from the Guides Page which has the info you will need:
The Audio Probe Explained – courtesy of Tonmann, Billy, Wilkie and Bruce
Continuity should be present from the battery supply to the current limiting resistor. That would not explain “no sound” and only affect the functioning of the LED. I am curious if you eventually populated R12 with at least a Jumper as I mentioned in my 1st reply since that would cause “no sound”.
If you have some photos of your build that are current it would be worth us having a look.