Issue with Bus protocol on Dell R740xd

We have an issue with one of our Dell R740xd servers where the installed drives are not showing. After a bit of digging, i found that the Bus protocol is showing as PCIe, whereas another of our R740xd servers is showing as NVMe. The drives are the same, albeit one is "Dell Ent NVMe AGN MU U.2 3.2TB" with device protocol NVMe 1.3(doesn't show) and the ones on the working server are "Dell Express Flash PM1725a 3.2TB SFF" device protocol NVMe 1.2 which are showing.

I did some reading on the issue and found that it should support either protocol. I didnt find much on the drives, but would assume they should work given the size of them is the same.

Some advice would be appreciated.

Thanks,

Steven