You should contact your Autodesk reseller and they will be able to search that serial number to find out if it goes to a different application or version. Most of the occurrences I've seen like this is almost always related to incorrect versions.
Hope this make sense.
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Darin Green
Director of Customer Support
Synergis Engineering Design Solutions
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HI Brandon and welcome to the community!
Confirming what Darren said in that invalid serial number errors are typically associated with using license information that has been upgraded to a newer version.
Outside of contacting your Authorized Reseller, our Registration and Activation team can also provide a full license report via the License Assistance Form.