terraform validation error despite changing the character count

Question

I am facing with the below error but upon checking, i have realized and reduced the characters to less than 20character for the name but I am still getting the same error. Any help would be appreciated.

Main.tf:

resource "aws_autoscaling_group" "scan_tool_scan_input_asg" {
  availability_zones = ["${split(",", var.availability_zones)}"]
  name = "${var.scan_tool_asg_name}-${var.build_number}"
  health_check_grace_period = "900"
  health_check_type = "ELB"
  max_size = "${var.asg_max}"
  min_size = "${var.asg_min}"
  desired_capacity = "${var.asg_desired}"
  force_delete = true
  launch_configuration = "${aws_launch_configuration.scan_tool_scan_input_lc.name}"
  vpc_zone_identifier = ["${split(",", var.subnet_id)}"]

VARIABLES:

# ASG
scan_tool_asg_name = "abcd_efg_sdfwdf"
scan_tool_instance_name = "input-database"
scan_tool_vpc_id = "vpc-xxxxxxxxx"
instance_type = "m5.large"
security_group = "sg-xxxx,sg-xxxxxxxx,sg-xxxxxxxx"
availability_zones = "us-east-1c,us-east-1d,us-east-1a"
subnet_id = "subnet-xxxxxxxx,subnet-xxxxxxxx,subnet-xxxx"
asg_max = "1"
asg_min = "1"
asg_desired = "1"
scan_tool_lc_name = "input_cp"
scan_input_health_port = "8080"

error:

Error retrieving AutoScaling groups: ValidationError: 1 validation error detected: Value '[]' at 'autoScalingGroupNames' failed to satisfy constraint: Member must satisfy constraint: [Member must have length less than or equal to 255, Member must have length greater than or equal to 1, Member must satisfy regular expression pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*]

Thanks