I assume USB? Cheap USB capture cards tend to be random in what actually works or doesn't.
A common trick is to put a USB 3 connector on it, and play up how much better USB 3 is than USB 2......and then put a USB 2 chip behind that connector so that you're limited to USB 2 anyway! So, guaranteed lossy compression *in the card*, just to cram "HD" video through USB 2, and possibly some other tricks or half-baked hacks that barely work.
I had 4 cheap USB cards in one rig and 1 in a different one, before I figured that out. My audio always came from elsewhere, so I never tested that from those capture cards.
Now I have a name brand for that 1, that actually *is* USB 3, and a 4-input PCIe for the other one. Much better all around! And I do get audio from at least the USB one. Still haven't tried the PCIe, but it says it does and my computer recognizes it as 4 audio inputs that I keep muted.