Could your kernel have changed between builds?
Yesterday I rebuilt an x86_64 system using a slightly newer revision of nixpkgs. The system appears to freeze during boot. (What actually happens is that the process responsible for switching from (or maybe to) the kernel framebuffer display system is hung.)
That same system config built using nixpkgs from last week worked fine. In fact, that same config using nixpkgs from today works fine. (I’m tracking nixpkgs branch nixos-22.11.)
Maybe if you just rebuild yet again your system will magically work. 