You have what we call an "old" licence. Old licenses were tied to various things depending on the license type.
It looks like your license was tied to a specific name of the assembly that can call Aspose.Word. I mean the license type was that only one application could call Aspose.Word.
For example it was licensed to "MyApplication", in this case only an executable or an assembly which has the following line in AssemblyInfo.cs can call Aspose.Words:
To resolve the issue, you need to make sure you have that attribute in the assembly that calls Aspose.Words and that the name matches the one that was specified when you ordered.
Aspose.Words have advanced so much since 1.9.9 and new licenses are much less restrictive so I really recommend you upgrade to latest Aspose.Words if possible. Please talk to sales if you are interested, there are good discounts for upgrades.