React User Registeration Page Erorr

Question

I have a react front end user registration page for my web app and i'm getting error in console saying POST  400 (Bad Request) and Error during registration: InvalidLambdaResponseException: Unrecognizable lambda output. My user data us being sent to cognito and dynamodb and all backend is working correctly but on the front end i'm getting that erorr. Any suggestions?

Answer

Check Userpool whether it has pre-sign-up lambda enabled. 
If so, the check the lambda return value. 
https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-sign-up.html

This is the best guess based on the symptoms described.

Providing more details around the errored API and its console log might be helpful.

React User Registeration Page Erorr

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