According to these pictures, you have inserted the flexible pcb (cable) upside down (pay attention to the contacts):
You should correct this, and try it again. Please also note the following comment in the linked thread regarding the correct insertion of the M.2 NVMe SSD.
Additional be ensure that you chosen a M.2 NVMe SSD (Key-M) not M.2 SATA SSD (Key-B and Key B&M). The maximum power consumption of the NVMe must not exceed 5 W.
Thanks, I fixed the cable and the drive is visible as PCI device, it is visible in /dev. It seems to be ok.
What puzzles me, is that nvme --list does not show it. Is it expected?
As long the device is listed with lsblk and can be used with parted, it’s looking good to me. You can also check the kernel log for messages regarding NVMe and PCIe if there is some issue remains.
sudo dmesg -T | egrep -i "NVMe|PCIe"
It’s possible that nvme-cli/libnvme does not support the NVMe model you have selected.
Strange, but after some time nvme --list shows the device. Maybe it needed a reboot, IDK.
Thank you for the help
Just a note: it would be great for the manual to beter describe which way to mount flexible PCB, or put connectors on the both sides of the PCB.
If only the first column with /dev/nvme.. was populated maybe you only missed the sudo command because nvme must be started with root permissions to get the information.