Office 2016 not validating
If you purchased the Microsoft Office 2016 APP from online store, the product code to active Office 2016 would be sent to you with an email receipt.
Check for the email came with "Microsoft", maybe it's in the spam, bulk, or junk mail folders.
If your Office product is one of the follow, you have an Office for home product.
This can be an Office 365 subscription, or a one-time purchase of Office or individual Office application.
Validation on a form You can use the Validation Rule property of a control on a form to specify a criterion that all values input to that control must meet.
In addition, with Office for business plans only admins responsible for managing Office 365 in their organization can do certain tasks.
Therefore, admins should view the issues and solutions listed under both the Office for business and Office 365 Admin tabs.
You also can check the full product keys with the VBScript code. Type the VBScript code to a notepad, and save it as a file. Double-click on the file to run, and click on the OK button to check product key for your Office 2016.
More detail info about checking Office product key with VBScript code, see: How to find your office product key after installation on computer.