S3 static website domain not working

This could be due to many reasons and it is difficult to provide a proper answer without having more details. I would recommend following the below procedure.

a. First ensure the S3 bucket is properly configured to host a static site. This is a long shot but can start there. b. But my guess is it could be related to Route 53. I realised that you are using an A record but since there is an internal resource I think you will have to use an alias record. Refer below.

https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/RoutingToS3Bucket.html