First, check your dmesg and see if there is any error.

Second, ensure you have the NVMe kernel drivers enabled. They are not the same as PCI drivers; you should be able to grep your kernel config for that. Something like this (from my NanoPi R6s with Armbian):

# zcat /proc/config.gz | grep -i nvme

# NVME Support

CONFIG_NVME_KEYRING=m

CONFIG_NVME_AUTH=y

CONFIG_NVME_CORE=y

CONFIG_BLK_DEV_NVME=y

CONFIG_NVME_MULTIPATH=y

# CONFIG_NVME_VERBOSE_ERRORS is not set

CONFIG_NVME_HWMON=y

CONFIG_NVME_FABRICS=m

CONFIG_NVME_FC=m

CONFIG_NVME_TCP=m

CONFIG_NVME_TCP_TLS=y

CONFIG_NVME_HOST_AUTH=y

CONFIG_NVME_TARGET=m

CONFIG_NVME_TARGET_PASSTHRU=y

CONFIG_NVME_TARGET_LOOP=m

CONFIG_NVME_TARGET_FC=m

CONFIG_NVME_TARGET_FCLOOP=m

CONFIG_NVME_TARGET_TCP=m

CONFIG_NVME_TARGET_TCP_TLS=y

CONFIG_NVME_TARGET_AUTH=y

# end of NVME Support

# CONFIG_NVMEM_REBOOT_MODE is not set

CONFIG_RTC_NVMEM=y

CONFIG_NVMEM=y

CONFIG_NVMEM_SYSFS=y

CONFIG_NVMEM_LAYOUTS=y

# CONFIG_NVMEM_LAYOUT_SL28_VPD is not set

# CONFIG_NVMEM_LAYOUT_ONIE_TLV is not set

CONFIG_NVMEM_RMEM=m

CONFIG_NVMEM_ROCKCHIP_EFUSE=m

CONFIG_NVMEM_ROCKCHIP_OTP=m

CONFIG_NVMEM_SPMI_SDAM=m

CONFIG_NVMEM_U_BOOT_ENV=m

On my VisionFive2 with the self-built 6.6.0 kernel, it looks like this:

# zcat /proc/config.gz | grep -i nvme

# NVME Support

CONFIG_NVME_CORE=y

CONFIG_BLK_DEV_NVME=y

CONFIG_NVME_MULTIPATH=y

# CONFIG_NVME_VERBOSE_ERRORS is not set

CONFIG_NVME_HWMON=y

CONFIG_NVME_FABRICS=y

# CONFIG_NVME_FC is not set

# CONFIG_NVME_TCP is not set

# CONFIG_NVME_AUTH is not set

CONFIG_NVME_TARGET=y

CONFIG_NVME_TARGET_PASSTHRU=y

CONFIG_NVME_TARGET_LOOP=y

# CONFIG_NVME_TARGET_FC is not set

# CONFIG_NVME_TARGET_TCP is not set

# CONFIG_NVME_TARGET_AUTH is not set

# end of NVME Support

# CONFIG_NVMEM_REBOOT_MODE is not set

CONFIG_RTC_NVMEM=y

CONFIG_NVMEM=y

CONFIG_NVMEM_SYSFS=y

# CONFIG_NVMEM_LAYOUT_SL28_VPD is not set

# CONFIG_NVMEM_LAYOUT_ONIE_TLV is not set

# CONFIG_NVMEM_RMEM is not set

# CONFIG_NVMEM_SPMI_SDAM is not set

CONFIG_NVMEM_U_BOOT_ENV=y

What sticks out is CONFIG_BLK_DEV_NVME - this sounds to me like the block-device support itself.

As for flashing firmware itself, that is very vendor-specific... afaik, there is a particular program for that to do exactly this. Look up how flashing firmware on Samsung SSD works; there was a huge problem with the firmware, this should have caused a lot of flashing guides to pop up.

Beyond that... i got nothing. Hope it helps tho!