this is my cloudwatch alarm:

resource "aws_cloudwatch_metric_alarm" "dms_replication_x_target_latency_increased_alarm" {
  alarm_name          = "DMSReplicationXTargetLatencyIncreased"
  comparison_operator = "GreaterThanThreshold"
  evaluation_periods  = "1"
  metric_name         = "CDCLatencyTarget"
  namespace           = "AWS/DMS"
  period              = "900"
  statistic           = "Maximum"
  threshold           = 300
  alarm_description   = "This alarm was created to detect whether X replication is being delayed for 300 secs in 15 minutes period."
  alarm_actions = [
  "arn:aws:sns:eu-central-1:123:cloud-watch-alarm"]
  
  dimensions = {
    "ReplicationInstanceIdentifier" = aws_dms_replication_instance.dwh_replication_instance_major_tasks.replication_instance_id
    "ReplicationTaskIdentifier"     = split("task:", aws_dms_replication_task.replicate_x_to_datalake_aurora3.replication_task_arn)[1]
  }
}

if I check the cloud watch metric on the DMS console, I see that the
CDC latency target value was more than 300 for almost 9 hours. However, the alarm did not run. when I check the alarm configuration, it says “Insufficient Data”. Why is this so? The alarm was created 3-4 days ago so there should definitely be data.

What am I missing out on?