Nixos install results in error during boot of "Timed out waiting for device /dev/dis/by-uuid/... to appear" with external NVME drive via USB

I have an issue when using an external NVME drive, grub successfully boots but once entering the entry default configuration (nixos generation) it gives me the below error: > "Timed out waiting for device /dev/dis/by-uuid/... to appear" I've double checked the UUID of the / partiton and it correctly matches what is in /etc/fstab and hardware-configuration.nix (which got generated with nixos-generate-config). In the grub recovery console if I do a ls -l I can see the partition with the correct UUID as well. I've also added "nvme" to boot.initrd.availableKernelModules. I'm able to nixos-enter the system via an external "live usb" with no issue. I suspect I need an additional initrd kernel module to be able to boot this, but I'm not sure which one? I've tried: 1. Adding these modules (got these from https://help.ubuntu.com/community/BootFromUSB) :

usbcore
sd_mod
ehci_hcd
uhci_hcd
ohci_hcd
usb_storage
scsi_mod

which still results in the same error. 2. Copying the partition to the internal drive (as opposed to the external NVME drive which still results in the same error.