Given command to run app doesn't work

[SnowCat007]

I tried running the command through the terminal on NixOS and it gave me the error of not allowing experimental commands to be run. Not a problem, I used the command to allow it to run experimental commands (nix --extra-experimental-features run github:polygon/gpt4all-nix) and it still didn't run the command saying

warning: unknown experimental feature 'run' error: 'github:polygon/gpt4all-nix' is not a recognised command

I tried 'sudo' because, well every linux problem comes down to sudo, but still nothing. I even tried cloning the repo and running the command again just in case the command only ran with the file locally available, but still the same error. I'm currently running the latest version of NixOS which is fully up to date. Is the command written wrong? Or should I go chat with the Nix devs to figure out what's going on with the 'run' command?

Thanks for taking the time to read this, I really hope to see this app working soon. Best regards. :)