Cloudwatch Rule Failed Invocation

Hi All,
I am new to the AWS services. I am trying to invoke a lambda through a cloudwatch event rule. The rule gets triggered in the specified time; but it fails to invoke the function. I understand that there are several criteria that could cause this. But where can I find which particular reason that caused the invocation failure. Is there a log somewhere or any other means? All I can see now is that the rule failed to invoke the lambda in the specified time.

Having said that, I create both the cloudwatch event and lambda using ansible. The invocation used to work sometimes. But when it fails, I want to know why it did. When the lambda is invoked and there is a failure within the lambda, I can go into the logs to get the reason. But the invocation failure is clueless.

And after creation, when I click on the target (from the cloudwatch event rule), it takes me to the right lambda and the lambda lists the cloudwatch event rule that (is supposed to) trigger(s) the lambda . As far as I can see the lambda policy includes the cloudwatch event rule in question.

Please let me know if I am missing anything or you need more information in this regard.

Thanks