Security Hub with Chatbot not receiving response from Custom Resource

Question

I'm following this tutorial on enabling aws security hub with aws chatbot. I seem to be having an issue with deploying the custom resource named AddCustomActionSHResource1 in the following code, which is linked from the tutorial to here.

AWSTemplateFormatVersion: "2010-09-09"
Description: Deploys CustomAction in SecurityHub to enable sending findings to Slack via AWS Chatbot
 
#==================================================
# Parameters
#==================================================
Parameters:
  SlackWorkSpaceID:
    Description: Slack workspace ID (Copy and Paste from AWS Chatbot Configured Clients Interface)
    Type: String
    MinLength: 9
    MaxLength: 15
    AllowedPattern: ^[a-zA-Z0-9_]*$
    ConstraintDescription: |
      Malformed Input Parameter: Environment must contain only upper and numbers. Length should be minimum of 9 characters and a maximum of 15 characters.
 
  SlackChannelID:
    Description: Slack Channel ID
    Type: String
    MinLength: 9
    MaxLength: 15
    AllowedPattern: ^[a-zA-Z0-9_]*$
    ConstraintDescription: |
      Malformed Input Parameter: Environment must contain only upper and numbers. Length should be a minimum of 9 characters and a maximum of 15 characters.
      
 
  # CustomActionName:
  #   Description: Name of the Custom Action in SecurityHub
  #   Type: String
  #   AllowedPattern: ^[a-zA-Z0-9_]*$ 
  #   Default: Send_To_Slack
  #   #Default: 'Send To !Sub "${ChatApplication}"'
 
 
#==================================================
# Resources
#==================================================
Resources: 
  #======================================================
  # Lambda Role to create Custom Action
  #======================================================
  LambdaIAMRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Action:
            - sts:AssumeRole
            Effect: Allow
            Principal:
              Service:
              - lambda.amazonaws.com
        Version: 2012-10-17
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/AWSLambdaExecute
      Path: /
  #======================================================
  # Lambda Policy to create Custom Action
  #======================================================
  LambdaIAMPolicy:
    Type: AWS::IAM::Policy
    DependsOn: LambdaIAMRole
    Properties:
      PolicyName: LambdaCreateCustomActionPolicy
      PolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Action:
              - 'securityhub:CreateActionTarget'
            Resource: '*'
      Roles: 
        - !Ref LambdaIAMRole
  #======================================================
  # Lambda Function to create Custom Action
  #======================================================              
  LambdaCreateCustomAction:
    Type: AWS::Lambda::Function
    DependsOn: LambdaIAMPolicy
    Properties:
      FunctionName: addcustomactionsecurityhub
      Description: CreateCustom Action in SecurityHub
      Runtime: python3.7
      Handler: index.lambda_handler
      Code:
        ZipFile: |
          import boto3
          import cfnresponse
          def lambda_handler(event, context):
            securityhub = boto3.client('securityhub')
            response = securityhub.create_action_target(Name="Send_To_Slack",Description='Send Messages to ChatApplication via AWS ChatBot',Id='SendToSlack')
            responseData = {}
            responseData['Data'] = response
            cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData, "CustomResourcePhysicalID") 
      MemorySize: 128
      Timeout: 10
      Role: !GetAtt LambdaIAMRole.Arn  
  #======================================================
  # Custom Resource to Invoke the Lambda Function
  #======================================================     
  AddCustomActionSHResource1:
    Type: Custom::AddCustomActionSH
    DependsOn: LambdaCreateCustomAction
    Properties:
      ServiceToken: !GetAtt LambdaCreateCustomAction.Arn
  #======================================================
  # SNS Topic
  #======================================================         
  SNSTopicAWSChatBot:
    Type: AWS::SNS::Topic
    Properties:
      DisplayName: AWS Chatbot SNS Topic
  EventTopicPolicy:
      Type: AWS::SNS::TopicPolicy
      Properties:
        PolicyDocument:
          Id: topicPolicyCustomaction
          Statement:
          - Effect: Allow
            Principal:
              Service: events.amazonaws.com
            Action: 'sns:Publish'
            Resource: '*'
        Topics:
          - !Ref SNSTopicAWSChatBot
  #======================================================
  # CloudWatch Event Rule
  #======================================================        
  EventRuleCustomAction: 
    Type: AWS::Events::Rule
    Properties: 
      Description: "SecurityHub Chatbot CustomAction"
      EventPattern:
        source: 
          -  "aws.securityhub"
        detail-type: 
          - "Security Hub Findings - Custom Action"
        resources:
          - !Sub 'arn:aws:securityhub:${AWS::Region}:${AWS::AccountId}:action/custom/SendToSlack'
      State: "ENABLED"
      Targets: 
        - 
          Arn: 
            Ref: "SNSTopicAWSChatBot"
          Id: "OpsTopic"
  ChatBotManageIAMRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument: 
        Version: "2012-10-17"
        Statement: 
          - 
            Effect: "Allow"
            Principal: 
              Service: 
                - "sns.amazonaws.com"
            Action: 
              - "sts:AssumeRole"
  SlackChannelConfig:
    Type: AWS::Chatbot::SlackChannelConfiguration
    Properties: 
      ConfigurationName: securityhubnotification
      IamRoleArn: !GetAtt ChatBotManageIAMRole.Arn
      LoggingLevel: NONE
      SlackChannelId: !Ref SlackChannelID
      SlackWorkspaceId: !Ref SlackWorkSpaceID
      SnsTopicArns: 
        - !Ref  SNSTopicAWSChatBot                          

When deploying this cloudformation file to cloudformation in AWS, everything deploys successfully except for AddCustomActionSHResource1. The error message is:

CloudFormation did not receive a response from your Custom Resource. Please check your logs for requestId [18sa90d1-49s1-4as7-9fsc-b79ssd6csd9]. If you are using the Python cfn-response module, you may need to update your Lambda function code so that CloudFormation can attach the updated version.

I found some information on updating the lambda function by just adding comments to it, but I don't believe that's the issue. Most of the useful information I found was from this aws link.