Pirate Radio VU Meter Issues (with Spotify)

Hello! I just built my pirate radio and it is working well, but the VU meter doesn’t function when streaming spotify.

The LEDs work just fine when I play audio from my shell, so it’s likely I just don’t have something configured correctly.

I followed the instructions in this tutorial:

Did I miss something obvious? Is there a good way to start troubleshooting this?

Additionally, I get some loud pops when I start any sort of playback, and (for example) espeak gives me a bunch of stderr output.

Anyone have a similar experience or some advice?