You are welcome.
I would try the following
- ensure your .sops.yaml file is in /etc/nixos/
- ensure that “agelong-string-key” has the value of your age public key
- then make sure you have a directory called secrets in /etc/nixos/
- then try making a secrets file: sops secrets/test.yaml
- remove all the example content and add: test: “test secret value”
- save the file
Does that work?