Having difficulty creating pipeline with a source input and an S3 input to a windows build machine

Question

I have modified a working configuration where the source is pulled from github, and then built on a windows build machine. I also need an S3 resource to be copied from a bucket. I have gone round and round with trying different things. The following configuration seems to be right according to all of the documentation I have read, but I still don't have access to the secondary source.

Here is my Cloudwatch Formation template file:

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  CareGaugeOneClientBuild:
    Type: AWS::CodeBuild::Project
    Properties:
      Source:
        Type: CODEPIPELINE
        BuildSpec: devops/buildspec.yml
      Visibility: PRIVATE
      Name: caregaugeoneclient-build
      Environment:
        Type: WINDOWS_SERVER_2019_CONTAINER
        PrivilegedMode: false
        ImagePullCredentialsType: CODEBUILD
        Image: {Not shown for example}
        ComputeType: BUILD_GENERAL1_MEDIUM
      ServiceRole: {Not shown for example}
      Artifacts:
        Type: CODEPIPELINE
      LogsConfig:
        CloudWatchLogs:
          GroupName: {Not shown for example}
          StreamName: build
          Status: ENAB  LED
  GreyhavensPipelineDevCareGaugeOneClient:
    Type: AWS::CodePipeline::Pipeline
    Properties:
      Name: dev-client-example
      ArtifactStore:
        Type: S3
        Location: {Not shown for example}
      RoleArn: {Not shown for example}
      Stages:
      - Actions:
        - ActionTypeId:
            Category: Source
            Owner: AWS
            Provider: CodeStarSourceConnection
            Version: 1
          Configuration:
            BranchName: master
            ConnectionArn: {Not shown for example}
            FullRepositoryId: {Not shown for example}
            OutputArtifactFormat: CODE_ZIP
          InputArtifacts: []
          Name: Source
          Namespace: SourceVariables
          OutputArtifacts:
          - Name: SourceArtifact
          Region: us-east-2
          RunOrder: 1          
        - ActionTypeId:
            Category: Source
            Owner: AWS
            Provider: S3
            Version: 1
          Configuration:
            PollForSourceChanges: 'true'
            S3Bucket: example-secrets
            S3ObjectKey: CodeSign.pfx
          InputArtifacts: []
          Name: FetchExampleBuildCert
          OutputArtifacts:
          - Name: ExampleBuildCert
          Region: us-east-2
          RunOrder: 2
        Name: Source
      - Actions:
        - ActionTypeId:
            Category: Build
            Owner: AWS
            Provider: CodeBuild
            Version: 1
          Configuration:
            EnvironmentVariables:
                '[{"name":"COMMIT_ID","value":"#{SourceVariables.CommitId}","type":"PLAINTEXT"}]'
            ProjectName: example-build            
            PrimarySource: SourceArtifact
          InputArtifacts:
          - Name: SourceArtifact
          - Name: ExampleBuildCert
          Name: Build
          Namespace: BuildVariables
          OutputArtifacts:
          - Name: BuildArtifact
          Region: us-east-2
          RunOrder: 1
        Name: Build
      - Actions:
        - ActionTypeId:
            Category: Build
            Owner: AWS
            Provider: CodeBuild
            Version: 1
          Configuration:
            ProjectName: example-cd
          InputArtifacts:
          - Name: BuildArtifact
          Name: Deploy
          OutputArtifacts: []
          Region: us-east-2
          RunOrder: 1
        Name: Deploy

I have renamed many of the objects in the yml file, but again this is a working configuration other than the S3 secondary artifact.

Here is my buildspec.yml file:

version: 0.2

env:
  variables:
    SOLUTION: .\example.sln
    PACKAGE_DIRECTORY: .\packages
    DOTNET_FRAMEWORK: 4.8

phases:
  pre_build:
    commands:
      - 'mkdir C:\BuildArtifacts'  # Create a directory to store the copied file
      - 'echo $env:CODEBUILD_SRC_DIR_ExampleBuildCert'
      - 'dir -s $env:CODEBUILD_SRC_DIR_ExampleBuildCert/*.pfx'

Note that while I see all of the code in both $env:CODEBUILD_SRC_DIR and $env:CODEBUILD_SRC_DIR_ECBuildCert, I don't find the secondary artifact.

Ideas?