PCP + Pi Zero W Analog Audio Out

Hi, i am using PCP 4 Beta 7 and I used this tutorial to build a small circuit to power an active speaker of mine.
Only problem: I do not hear a thing. In the squeezelite settings I set analog audio as output, I edited the /boot/config.txt and inserted the line
The circuit is one channel only and connected to gpio 18. I verified several times that the circuit is correct and all the connections are correct. Is there something else that has to be considered using PCP?

Second question: Since I only power one speaker, how can I configure PCP to output mono sound?

Thanks in advance