When I try to use Office 365 it wants a product key, never had one.

Hello, thank you for reaching out to Microsoft Q&A.

It appears that you have purchased the Office 365 Personal subscription directly from Microsoft, in which case you will not receive a product key. Instead, the license will be digitally assigned to your Microsoft account. Your Microsoft account will handle the activation.

On the screen where it asks you to enter the product key, do you see an option to sign in instead? If so, please sign in using the same Microsoft account that you used for the purchase. This will activate Office on your device.

(Or)

Uninstall all the previous versions of Office apps installed on your device and then reinstall them.

To uninstall office, use the Office uninstall troubleshooter here-

https://aka.ms/SaRA-officeUninstallFromPC

Once uninstalled, go to your Microsoft account Services & Subscriptions page to reinstall Office.

https://account.microsoft.com/services

• Once installed, open any Office apps such as Word or Excel and sign in with your Microsoft account to activate Office apps.