Error on run: Property validation failure: [Value of property {/Targets/0/Values} does not match type {Array}]

Question

This CF is being created in YAML not JSON.

I am building Systems Manager Maintenance Windows, Targets and Tasks through Cloudformation.

When creating the stack, the Resources: MaintenanceWindow: section complete successfully. It's the next section (below) that is failing. Not sure about the last section as we never get there.

Here is the location for the full template: https://pastebin.com/DNEkLPGS

I have tried using validators and everything (YAML and the CloudFormation Validators) and everything comes back as good.

Here is the section giving errors:

Parameters:
  MaintenanceTargetName:
    Description: Maintenace Target Name (No Spaces)
    Type: String
  MaintenanceTargetDescription:
    Description: Sample - UAT Servers
    Type: String
    MaxLength: '128'
  MaintenanceTargetTarget:
    Description: Tag Key should equal 'AgentUpdate'
    Type: String
    Default: tag:AgentUpdate
  MaintenaneTargetKeyValue:
    Description: True or False
    Type: String
    Default: True
    AllowedValues:
      - True
      - False

Resources:
  MaintenanceWindowTarget:
    Type: 'AWS::SSM::MaintenanceWindowTarget'
    Properties:
      WindowId: !Ref MaintenanceWindow
      ResourceType: INSTANCE
      Targets:
        - Key: !Ref MaintenanceTargetTarget
          Values: !Ref MaintenaneTargetKeyValue
      Name: !Ref MaintenanceTargetName
      Description: !Ref MaintenanceTargetDescription

Running the template gives the following error:

MaintenanceWindowTarget | CREATE_FAILED | Property validation failure: [Value of property {/Targets/0/Values} does not match type {Array}]

Answer 1

Found the issue, it was a formatting problem:

Resources:
  MaintenanceWindowTarget:
    Type: 'AWS::SSM::MaintenanceWindowTarget'
    Properties:
      WindowId: !Ref MaintenanceWindow
      ResourceType: INSTANCE
      Targets:
        - Key: !Ref MaintenanceTargetTarget
          Values: !Ref MaintenaneTargetKeyValue
      Name: !Ref MaintenanceTargetName
      Description: !Ref MaintenanceTargetDescription

The issue lied in the Targets section:

      Targets:
        - Key: !Ref MaintenanceTargetTarget
          Values: !Ref MaintenaneTargetKeyValue

The above was incorrect. Below is the correction:

      Targets:
        - Key: !Ref MaintenanceTargetTarget
          Values: 
          - !Ref MaintenaneTargetKeyValue

Hope this helps others!!