Pico Explorer audio not working

The explorer demo code appears to work except for the audio. I’ve put a jumper from GP0 to Audio but no sound comes out. Any ideas?

MicroPython e7cde34 on 2021-02-08; Raspberry Pi Pico with RP2040

Thanks for the help!

It is very quiet on mine.

Is there a way to turn audio on a pin OFF. Does freq = 0 do this in tone?