Adobe Acrobat XI pro installation serial number INVALID

Here is a link that may help find a solution:
https://helpx.adobe.com/au/creative-suite/kb/error-serial-number-valid-product.html

Otehrwise. try contact an Adobe agent through live chat. The Adobe Support Help Centre, where you can access an online chat link is in the above page or directly at: https://helpx.adobe.com/support.html

Make sure that your browser does not block scripts, or pop-ups, and also make sure your browser allows cookies for the link to work, If you don't see the chat icon in the bottom right, or it won't open the chat, try another browser (or change the browser settings).

Type  'Agent' in the chat box to bypass the chatbot and be connected to a real person.
- https://helpx.adobe.com/contact.html?rghtup=autoOpen

I'm adding a warning to take care with any messages or people contacting you claiming to be Adobe. This sometimes happens. Adobe does not provide support by email, so beware of any message in this format. More information about scammers can be seen in the link below:
https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-com...