After all configuration and deployments have completed, navigate to the HTTPS Amazon CloudFront endpoint generated from the AWS SAM template. You should be redirected to your IdP to perform Authentication.
If you encounter an HTTP 4xx or HTTP 5xx error, trying opening up a new browser or browsing in private mode. Sometimes there may be cached configurations that are causing the problems.
If there are issues, ensure that all IdP configurations are set up correctly, including the Callback URIs.
Ensure that the correct AWS Secrets Manager Secret name in use which is "cloudfront/DISTRIBUTION_ID" Also, ensure that the Key-Value pair is set up correctly in AWS Secrets Manager including a Base64-encoded value that is the JSON configuration.
If using an AWS Customer-Managed KMS Key, ensure that the Lambda@Edge Function Execution role is in the list of KMS key users.