This has stopped recently – perhaps due to the hot weather. When I try to start it its says there is not output device which is the HiFiBerry Digi card. HiFiBerry is not available as a soundcard in the advanced options of Squeezelite. Do you think the soundcard has died?
I have another similar installation where it continues to work. This location was considerably cooler.
Maybe the sound card really did burn out, at least it doesn’t seem to be recognised any more. Try disconnecting the sound card from the Pi and reconnecting it. Select „none“ as the sound card in the HiFiBerry plugin, restart the device, then select the HiFiBerry Digi again and restart again. If it is still not recognised, it is probably defective. Of course, you can also exchange the sound cards of your two devices to see which component is defective.
Luckily it did not burn out but just overheated I think. I took the case off and stopped using the Pi on the hottest days. I also had problems with Amazon Fire TV sticks and there is no easy way to ventilate those.