I recently replaced my faulty old Raspi 3B with a 3B+, attached the two HATs I've got (a JustBoom DAC HAT sound card and an S.USV Advanced), plugged the SD card into the new one, upgraded the Raspbian (Buster), and can't bring the sound card back to life! It's no longer recognised by the system, neither does the red LED go on:

```
pi@autoradio:~ $ aplay -l
aplay: device_list:272: no sound cards found ...

```

I can't find any sound card related warnings in `dmesg`. Here's the list of loaded sound-related modules:

```
pi@autoradio:/proc/device-tree/aliases $ lsmod | grep snd
snd_soc_pcm512x_i2c    16384  0
snd_soc_pcm512x        32768  1 snd_soc_pcm512x_i2c
snd_soc_justboom_dac    16384  0
snd_soc_bcm2835_i2s    16384  0
snd_soc_core          225280  3 snd_soc_justboom_dac,snd_soc_pcm512x,snd_soc_bcm2835_i2s
snd_compress           20480  1 snd_soc_core
snd_pcm_dmaengine      16384  1 snd_soc_core
snd_pcm               106496  5 snd_compress,snd_soc_pcm512x,snd_pcm_dmaengine,snd_soc_bcm2835_i2s,snd_soc_core
snd_timer              32768  1 snd_pcm
snd                    77824  5 snd_compress,snd_soc_pcm512x,snd_timer,snd_soc_core,snd_pcm
regmap_i2c             16384  2 rtc_ds1307,snd_soc_pcm512x_i2c

```

Tese are the relevant lines in `/boot/ocnfig.txt`:

```
dtparam=audio=off
dtoverlay=justboom-dac

```

…and this is the current Raspbian version:

```
pi@autoradio:~ $ uname -a
Linux autoradio 5.10.17-v7+ #1403 SMP Mon Feb 22 11:29:51 GMT 2021 armv7l GNU/Linux

```

With all peripherals disconnected and only the sound card + the UPS HAT attached, I get these I²C addresses. Both belong to the UPS, not to the sound card:

```
pi@autoradio:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- 0f 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

```

The card did work with the old Raspi, and save for the system upgrade I haven't changed anything on the O/S. So, why isn't my sound card being recognised any more?