[PROBLEM] No Output from Sound Card

[Nutul]

The link you provided lists the card as a PiFi + (Plus) and as it is derived/copied from the genuine HiFiBerry Digi+ (Plus) I would expect that the driver/overlay required is the HiFiBerry Digi Plus + and not the lower version HiFiBerry Digi.
Look again at the Moode settings and try the Digi Plus.

Note too the vendor lists this as compatible with Pi 3 and 2. No mention of Pi 4.

I have checked with my supplier and they say this card supports Pi4, or maybe they don't know. Still trying to figure out why there is no sound.

Of course till you're not sure 100% trying is good, but...
a) no mention by the manufacturer about Pi4 compat.
b) vendor possibly "doesn't know"
c) discrepancy in the driver's name Digi vs Digi+
d) still no sound from the card