Error importing into Postgres RDS from S3 file

I'm trying to use the aws_s3.table_import_from_s3 functionality and believe I have set everything up correctly according to: https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/USER_PostgreSQL.S3Import.html

However, when I run my command in Postgres, I am getting the following error:

NOTICE:  Attempting to validate pre-signed URL. 3 attempt(s) remaining. CURL error code 28 with message Failed to connect to <HOST> port 443 after 29885 ms: Couldn't connect to server.

Note, I am in a VPC so I'm not sure if there's something else that needs to be done in order for my Postgres instance to pull from the S3 bucket (other than permissions outlined in the doc above).