I have recently received a knockshield 2 and have started to get to grips with its complexities.
I tried to read all the documention but I did not get any output when using a single sensor input on pins 1 and 2.
I subsequently found that the silkscreen numbering of 1234 on the pcb is in fact 4321!
This is not a problem when the software is setup for two sensors as it will use the highest voltage and ignore the zero value. Looking a photographs of earlier knock shields , they look be correct. Interesting.
Onwards and upwards.
Roger