When you say certificates - what certificates do you mean? If you are referring to certificates used by OM server for server-agent communications then these certificates expire in 20 years from the time of issue. So there is no tool provided to alert on expiry.
Adding to Ram´s answer the only license that you might see that expires would be an evaluation License that will last for 6 months and once it is expired you will receive a message that the license has expired in order for you to add the permanent license.
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