AWS DMS Neptune target endpoint error

According to the following documentation for creating a target endpoint using AWS DMS https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.Neptune.html

The setup looks like as follows:

1. A Neptune DB cluster(without Notebook)
2. A DMS replication instance
3. A source endpoint (S3)
4. A role that has full access to S3, Neptune and RDS
5. A target endpoint (AWS Neptune) <-- This is the point of failure

After configuring the target endpoint when I click on "Run test" I see following error:

arn:aws:iam::12xxxxxx2:role/xxxx-dms-role role should be associated with xxx-cluster-xxx-neptune cluster.

Is there something missing?

The role is configured with policies that provide full access to all resources(especially Neptune and S3)

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:*"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": "neptune-db:*",
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": "rds:*",
            "Resource": "*"
        }
    ]
}