i need to reinstall office on a new machine

Which version of Office do you have? Note that if it is a perpetual (one-time payment) license such as Office 2021 or Office 2024, you may have to contact Microsoft support for the activation.

Note that all (recent) versions require that you install via your associated account at https://account.microsoft.com/services . You can't use the product key more than once.

This is awful, the "help app" doesn't work

You phone up and I just get the same automated garbage

use the activation app - doesn't work

activate online - doesn't work

AI is only useful for the majority, but tech companies are using AI for everything and there is nothing if the AI fails. This is going to be the future. If the AI response is wrong or doesn't work there will be no alternative. No one else to speak to, no help, no one to care. Just AI offering the same failing advice and then hanging up.

Try the appropriate phone number for your region from the article at https://support.microsoft.com/en-us/office/-telephone-activation-is-no-longer-supported-for-your-product-error-when-activating-office-9b016cd2-0811-4cb3-b896-5a6a13177713 .