Speaker phat not working (again?)

After struggling to get my speaker phat working a few months ago it’s now either died, or something’s changed in the software/distribution.
It’s the ‘usual’ problem of no sound but the vu meter leds are working fine.
Absolutely silent on boot, no clicks, nothing. That’s suspicious because it used to click a few times during booting.
aplay -l says no soundcards found.
Stopping pulseaudio has no effect (not a surprise).
The test.sh script says file not found because there’s no audio device and the only thing that works are the leds.
I swear it was working ok, sound and everything, together with a load of other phats on my phat stack.
Reinstalling the speaker phat config, software and python library using the curl one-liner didn’t fix it. Config, from what I remember, and from the other forum threads seems ok.
Installing for the first time on a pi3b+ has exactly the same problem, which could mean it’s dead.
I’ve even resoldered the gpio header on the speaker phat in a desperate attempt to get it working, but no joy there.
The hifiberry-dac appears in the lsmod list, so I assume it’s getting loaded correctly. Has anything changed in the dac or raspbian?
Has anyone tried using or installing a speaker phat recently with an up-to-date raspbian?
How could I tell if the dac hardware is probably still working or if it’s just dead?
Or what (stupidly obvious) thing have I forgotten?

Edit: No, I haven’t done a clean install on a new raspbian sd card. I’m getting annoyed with that as a possible solution…

The SN3218 LED driver uses i2c. The sound is I believe is I2S. Not sure how you check or test that though?
Pinout is here, https://pinout.xyz/pinout/speaker_phat# if that helps. Kind of sounds (no pun intended) like its failed?