Verify the .env File Ensure that your .env file contains the correct MongoDB URI and other environment variables. Example:

env Copy code MONGODB_URI=mongodb+srv://:@clustername.mongodb.net/?retryWrites=true&w=majority PORT=5000 Run a test using the mongo shell or MongoDB Compass:

bash Copy code mongo "mongodb+srv://:@clustername.mongodb.net/" --authenticationDatabase admin If this fails, verify the cluster's IP Whitelist and network access settings. telnet clustername.mongodb.net 27017