I have a HiFiBerry Digi+ Pro that's working great with my Pi 3B using Volumio. I have a 7" touchscreen connected, powered from the PI 5v.
I wanted to power this setup using PoE so I bought a HAT (this one). Everything powers up just fine, and the HiFiBerry as recognised as a sound device in the Volumio software, but no sound plays, just a very low volume intermittent digital noise.
Thinking maybe the setup is underpowered from PoE, I disconnected the 7" display. Same issue. I removed PoE and powered the stack with a Pi power brick. Same issue.
It seems that, when the HiFiBerry HAT is connected on top of the PoE HAT, it fails, and it's not looking like a power issue. I'm not finding very much on this issue online, apart from a few (older) success stories.
Any tips on what I could look at next?