# Troubleshoot errors when commanding Security Engines

There are several possible causes and solutions when you try to command an engine using the SMC Client and receive an error.

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For more details about the product and how to configure features, click Help or press F1.

## Steps

1. If there are disabled nodes in the same cluster, enable them before refreshing the policy.
2. Refresh the engine’s policy.
3. Read all messages displayed and make sure none of the nodes roll back to the previous policy.
4. If policy installation fails, see Troubleshooting Policy Installation.
   If policy installation fails and the status and statistics information displayed in the SMC Client is missing (status is displayed as unknown) even though the engine is online and processing traffic, the problem might be due to an expired certificate.