ClientError: An error occurred (InternalFailure) when calling the Publish operation (reached max retries: 4)

I am simply trying to publish to an SNS topic using a lambda function. The function code as follows, with ARN being the actual SNS topic ARN:

import boto3
print('Loading function')

def lambda_handler(event, context):
    client = boto3.client('sns')
    response = client.publish(
        TargetArn='ARN',   
        Message="Test",   
    )
    return response

The function execution role as access to SNS. In fact I even gave SNS full access. But I keep getting the error:

{
  "errorMessage": "An error occurred (InternalFailure) when calling the Publish operation (reached max retries: 4): Unknown",
  "errorType": "ClientError",
  "stackTrace": [
    "  File "/var/task/lambda_function.py", line 6, in lambda_handlern    response = client.publish(n",
    "  File "/var/runtime/botocore/client.py", line 316, in _api_calln    return self._make_api_call(operation_name, kwargs)n",
    "  File "/var/runtime/botocore/client.py", line 626, in _make_api_calln    raise error_class(parsed_response, operation_name)n"
  ]
}

I do not find any access denied errors in cloudtrail either. Any idea on what is the issue here ?

Edit: Its my bad, I used the subscription ARN instead of the topic ARN causing this issue.

Answer

In case if anyone is facing this issue, make sure you use the correct ARN – use the ARN of the Topic instead of the subscription.