Uncaught (in promise) Error:cb=gapi.loaded_0?le=scs:158 Uncaught (in promise) Error: Illegal url for new iframe - firebase auth service

I am using firebase for signup with Gmail service. When I use process.env.REACT_APP_FIREBASE_API_KEY

const firebaseConfig = {
   apiKey: process.env.REACT_APP_FIREBASE_API_KEY,
   authDomain: process.env.REACT_APP_FIREBASE_AUTH_DOMAIN,
   ...
}

I got an error saying that my domain is not registered, but when I used the key directly inside the config object it works as expected

const firebaseConfig = {
  apiKey: "Az**aS******97_4pSLLM2C*******72g*vcd****8",
  authDomain: "app-*******.firebaseapp.com",
  ...

How I can make sure that the process does work as expected