Boot causes kernel panic

Dear List,

I have just installed nixos on asus laptop N550LF. When I try and boot it with rEFIND boot manager it causes a kernel panic with the message " unable to mount root file system on unknown block". I am booting in UEFI mode.

Not sure how to fix the problem, as I followed the instructions to the letter I think.

All help appreciated.

TIA

Jackplug