Change operation type to POST resolves the problem because the symptom is specific to the automation subsystem handling APIC, Postman. Nexus automation failures are frequently caused by a missing EEM event statement, absent event-default action, invalid REST path, incorrect JSON or XML syntax, Guest Shell DNS/resource settings, or a scheduler feature that is not enabled. The selected answer corrects that execution prerequisite. The wrong options may make sense for normal switch forwarding, but they do not repair the automation control path. Cisco documentation treats Guest Shell as a separate Linux environment and EEM as a policy engine that can intercept CLI events; both must be validated from their own operational state. A proper verification is to confirm the policy is registered, run the job or API call again, review the response or syslog output, and ensure that normal CLI behavior is preserved after the automation fires.