Resolve AWS EC2 SSH Timeout

My production-grade Linux EC2 instance is up, its Elastic IP is in place, port 22 is open in the security group, and every VPC component—subnet, route table, NACL—checks out. Yet every SSH or nc attempt times out, and even EC2 Instance Connect refuses to talk... (Budget: ₹600 - ₹1500 INR, Jobs: Amazon Web Services, Cloud Computing, Linux, Network Administration, System Admin, System Administration, Technical Support, Troubleshooting)