Mongo/Mongoose will not pass a string

Attempting to connect to MongoDB via a follow-along, and I keep getting this error:

The uri parameter to openUri() must be a string, got "undefined". Make sure the first parameter to mongoose.connect() or mongoose.createConnection() is a string.

Here is the code I’m working with:
.env file (I changed the username and password. The name is cluster0)

MONGO_URI="mongodb+srv://username:password@cluster0.l94wepe.mongodb.net/?retryWrites=true&w=majority"

Server.js

dotenv.config();

mongoose
  .connect(process.env.MONGODB_URI)

  .then(() => {
    console.log("connected to db");
  })
  .catch((err) => {
    console.log(err.message);
  });

Any help is appreciated, let me know what other info I can provide. Thank you.

>Solution :

The .env file has "MONGO_URI" and the JS file has "MONGODB_URI"