Getting license validity or activation error for my Adobe Acrobat DC

Hello, 

I have a valid Adobe Acrobat DC Pro license Version 12 for students and teachers which Adobe no longer provides technical support. Since yesterday, whenever trying to convert a Word file to PDF, I get this error message:  "Your request could not be completed. Adobe Acrobat DC license has either expired or not been activated." I am using this product on Windows 10.

I appreciate any help!