Understand the Problem:
The inability of external users to log in indicates potential issues with configuration or permissions.
Review Cognito Configuration:
Check for recent changes in Cognito user pool settings, such as password policies or authentication flow configurations.
Ensure the app client settings (e.g., callback URLs, OAuth flows) are correctly configured.
Review IAM Policies and Role Trust Relationships:
Verify that IAM roles used by Cognito (e.g., for identity providers) have the correct policies attached.
Ensure trust relationships for roles are properly configured to allow Cognito to assume them.
Advantages of Reviewing Configurations:
Addresses the root cause of login failures without disrupting user experience (e.g., resetting passwords).
Next Steps:
If no issues are found in the configuration, proceed with detailed logging and monitoring using CloudTrail (Option A).
Troubleshooting Amazon Cognito User Pools
Configuring App Clients in Cognito
IAM Roles for Cognito
