How To Remove Product Activation Failed In Microsoft Office 2013 ((link)) -

Before you panic, understand that this error usually does not mean your license is invalid. It often stems from a corrupted activation cache, a server communication issue, or a mismatch between your installed version and the license key.

Encountering the "Product Activation Failed" error in Microsoft Office 2013 can be frustrating. You might see a red banner reading "Product Activation Failed" or "Unlicensed Product" across Word, Excel, or PowerPoint, often accompanied by a prompt to enter a product key. Before you panic, understand that this error usually