When I've had issues like that (although usually in consumer boards) SOMETIMES taping the two SMBUS connectors does the trick. You'll need some katon tape or similar, have it wrap *slightly* around the bottom to keep it from peeling off as you insert it and have it go up the card enough so it doesn't get stuck in the slot when pulling it out.Hope that this topic is not dead yet.
I recently both a Chinese card that supports two NVMe M.2 modules (link). Apparently, it is based on Asmedia ASM2812.
lspci sees the card as an upstream PCIe port with two downstream ports which matches the reality.
What's interesting is that the card works fine in a consumer motherboard, but it is not detected at all with X9CSM-F motherboard.
I tried both x8 slots of it with the same result.
The card (and an NVMe module on it) is not visible in the OS (lspci, etc) and I do not see any changes in the BIOS too.
I wonder why that could be and if anything could be done about that.
If that still doesn't work make sure you are using the same os on both boards to reduce variables, check that the slot works at all, and look in bios/eufi for any possible conflicting settings.