Some corporate firewalls block traffic to S3 endpoints. Try bypassing your VPN to rule this out.
If you are trying to download a file via a public URL (e.g., through a browser without signing in), AWS’s settings are likely the barrier. unable to download file from s3 bucket
If you are downloading from an EC2 instance, ensure your VPC endpoint for S3 is correctly configured and that the Route Table points to it. Quick Checklist for Success: Does the IAM user have s3:GetObject ? Is there a Deny statement in the Bucket Policy? Is the file in Glacier? (Restore it first). Is KMS encryption used? (Check kms:Decrypt permissions). Some corporate firewalls block traffic to S3 endpoints
(Use a Presigned URL if it is).