Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Try an in private (incognito) browser window to ensure that you are able to sign in to the correct account.
By the way, which particular Office 2016 do you have? Office Home & Business? Something else?
If you purchased Office as part of the HUP (Home Use Program) using a work e-mail, see https://www.microsoft.com/en-us/workplace-discount-program/order-history?msockid=1959934133e5636b18748711326a6224 .