Question graphics card not detected (on slot PCIe 3.0) when NVMe adapter is connected (on slot PCIe 2.0)

[spectacles]

Hi. How are ya?
I have an older computer at work, ASRock B75 Pro 3-M, with i5-3570, 16Gb of ram, a few SSDs, Nvidia GTX 970. Nothing special, it works fine.
Recently I decided I'd get my first NVMe drive. Didn't really need it, but I found a cheap one so I thought, I'd give it a try. Since the mobo doesn't support NVMes, I also bought an adapter.

The drive works and the adapter does as well. However, if the adapter is connected to the motherboard (with or without the drive), the 970 is non-existent, according to bios (I can actually see in bios which slots are occupied), even though it's connected. The onboard graphics card works fine (how I was able to see the driver and the adapter work).

The motherboard has 2 PCIe slots. Slot 1 is gen3.0 (where 970 is), slot 2 is gen2.0 (where the adapter is). I haven't gone so far as to put the 970 into slot 2, because the case led, on-off-reset etc. cables are in the way (the card doesn't go into the slot all the way). It would be a pain to turn the pc on without the on-off switch.

I've updated the bios to the latest version, no difference. Any thoughts on what I can do to make this work?

 

[helpstar]

Did you install the latest beta bios 2.00?

Which power supply are you using?

Try a minimum setup using only the boot drive, nvme and the GPU

Might be a compatibility issue, try a different nvme adapter compatible with pcie 2.0 x4 compatibility

Does the nvme drive actually work? We're you able to copy files or similar?

 

[spectacles]

Thanks for the reply. Yes, I have installed the latest beta bios 2.00. The power supply is a 450w LC6450GP2. I'll try the minimum setup as soon as possible (not at work right now). The 970 is working (the fans are spinning), but according to bios, it doesn't exist.
When everything is connected, the onboard graphics card works and I can use the computer normally. I've tested the drive, I get about 1.6Gb Read/1.4Gb Write transfer. It was bought 2nd hand, so there was some data on it, which I was able to delete. So the drive and the adapter are working as intended.

(The only thing I haven't tried is putting 970 into slot 2 and the adapter in slot 1. It would be a pain to do - I'd have to disconnect the on/off, reset etc. connectors and then figure out how to turn on the pc. It's gonna be the last thing I try).