Cannot get `sops.age.keyFile` to find my key

I am unable to get sops.age.keyFile to find my key. The key works: if I leave it in the default location (/home/phil/.config/sops/age/keys.txt) then I can open and decrypt secrets/secrets.yaml.

But if I set sops.age.keyFile = "/home/phil/keys.txt"; and move the key from .config/... to there, I keep getting the error “failed to load age identities: failed to open file: open /home/phil/.config/sops/age/keys.txt: no such file or directory”. The permissions for keys.txt are 600 the the owner is phil:users. I think that maybe I screwed up something between HM and sops, but I’m not sure.

My flake.nix looks something like:

{
  description = "phil NixOS configuration";

  inputs = {
    home-manager = {
      url = "github:nix-community/home-manager";
      inputs = {
        nixpkgs.follows = "nixpkgs";
      };
    };
    impermanence.url = "github:nix-community/impermanence";
    sops-nix.url = "github:Mic92/sops-nix";
    nixpkgs.url = "nixpkgs/nixpkgs-unstable";
  };

  outputs = inputs @ { self, home-manager, impermanence, nixpkgs, ... }:
    let
      homeDirectory = "/home/${username}";
      hostName = "phil-nixos";
      username = "phil";
    in
      {
        nixosConfigurations.${hostName} = nixpkgs.lib.nixosSystem {
          specialArgs = {
            inherit
              homeDirectory
              hostName
              username
            ;
          };
          system = system;
          modules = [
            ./configuration.nix
            impermanence.nixosModule
            home-manager.nixosModules.home-manager {
              home-manager.extraSpecialArgs = {
                inherit
                  homeDirectory
                  username
                ;
              };
              home-manager.useGlobalPkgs = true;
              home-manager.useUserPackages = true;
              home-manager.users.${username}.imports = [
                ./hm.nix
                (inputs.impermanence + "/home-manager.nix")
                inputs.sops-nix.homeManagerModules.sops
              ];
            }
          ];
        };
      };
}

MY hm.nix:

{
  pkgs
, homeDirectory
, username
, ...
}:

{
  home = {
    stateVersion = "24.05";
    username = username;
    homeDirectory = homeDirectory;
  };

  programs.home-manager.enable = true;

  home.packages = with pkgs; [
    sops
  ];

  sops.age.keyFile = "/home/phil/keys.txt";
}

Thanks for any help or guidance!