CVAT Installation in EC2 Instance

Did you follow the guides here? https://github.com/OperationalBina/Cvat/blob/master/cvat/apps/documentation/AWS-Deployment-Guide.md

Double-check you followed all steps. Make sure your instance's security group allows inbound on appropriate ports & sources. Make sure your instance subnet route table has a route to the Internet Gateway, and NACL has the default ALLOW rules for all traffic inbound & outbound, or if it's locked down, allows for outbound ephemeral ports.