MSK Connect - not connecting to MSK Cluster

From CloudWatch logs:

[Worker-08b99ad5f119f02cd] org.apache.kafka.common.errors.TimeoutException: Call(callName=fetchMetadata, deadlineMs=1683595748944, tries=1, nextAllowedTryMs=1683595749045) timed out at 1683595748945 after 1 attempt(s)

Security Group The MSK Connector uses the same security group as the MSK Cluster and accepts All Traffic from all ports inbound from itself.

IAM Role The MSK Connector uses an IAM role with the following trust relationship:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "kafkaconnect.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}

The same role has the following policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:Connect",
                "kafka-cluster:DescribeCluster"
            ],
            "Resource": [
                "cluster-arn"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:ReadData",
                "kafka-cluster:DescribeTopic"
            ],
            "Resource": [
                "ARN of the topic that you want a sink connector to read from"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:WriteData",
                "kafka-cluster:DescribeTopic"
            ],
            "Resource": [
                "ARN of the topic that you want a source connector to write to"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:CreateTopic",
                "kafka-cluster:WriteData",
                "kafka-cluster:ReadData",
                "kafka-cluster:DescribeTopic"
            ],
            "Resource": [
                "arn:aws:kafka:region:account-id:topic/cluster-name/cluster-uuid/__amazon_msk_connect_*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:AlterGroup",
                "kafka-cluster:DescribeGroup"
            ],
            "Resource": [
                "arn:aws:kafka:region:account-id:group/cluster-name/cluster-uuid/__amazon_msk_connect_*",
                "arn:aws:kafka:region:account-id:group/cluster-name/cluster-uuid/connect-*"
            ]
        }
    ]
}

This seems to cover everything I can find in docs / other re:Post threads.

Any help would be appreciated!