.env.development.local — !link!

# External Service Example SENDGRID_API_KEY=SG.test_key... AWS_ACCESS_KEY_ID=AKIA... AWS_SECRET_ACCESS_KEY=... AWS_REGION=us-east-1 S3_BUCKET=dev-uploads-bucket

You forgot the framework-specific prefix (like REACT_APP_ or VITE_ ). Fix: Rename your variable in the file. .env.development.local

Your backend database runs on port 5432 on the main server, but on your specific laptop, you changed it to 5433 due to a conflict. # External Service Example SENDGRID_API_KEY=SG