Render can't read my env value

Hi everyone

my project is react + django, the backend is work,
but frontend can’t read my env value, the require of react prefix I have did, could you help me to figure out?

and I don’t know why I can’t insert image to this post?
so I type the contend as below:

Render env Key: REACT_APP_LOGIN_URL

Coding Content:
const LOGIN_URL = process.env.REACT_APP_LOGIN_URL;
console.log('LOGIN_URL: ', LOGIN_URL);

Log Response: undefined