This article covers methods to resolve AWS s3 lambda 500 Internal Service Error.
Basically, this error occurs if Lambda function's resource-based policy doesn’t include permission for your API to invoke the function.
This error occurs if your Lambda function's resource-based policy doesn't include permission for your API to invoke the function.
When you build an API Gateway API with standard Lambda integration using the API Gateway console, the console automatically adds the required permissions. However, when you set up a stage variable to call a Lambda function through your API, you must manually add these permissions.
Finally, To verify that the error is caused by missing permissions, review your API's logs.