Can not Access variables of .env file

Question

In my React app, I was trying to access some variables from .env.local but every time I print It it shows undefined.

// src/.env.local
REACT_APP_SECRET_CODE=123456 

// In different component
console.log(process.env.REACT_APP_SECRET_CODE);

output: undefined

Note: I tried to use .env file as well, but did not work.

React Script version is 5.0.1