When you're trying to activate Office 2016 for Mac, you might receive this error:
Installation limit reached
Your account <email address> has been used to activate Office on the maximum number of computers allowed. Visit your account page to manage your settings and then return here to retry activation.
This error occurs when you've reached the maximum number of activations that Office allows.
Deactivate an Office 365 install
Office 2016 for Mac: One-time purchase
If you bought a one-time purchase of Office 2016 for Mac and not a subscription to Office 365, you are allowed only one install of Office 2016 for Mac. If for some reason you need to activate the same copy of Office again, you can do so over the phone. Use the link below to contact Microsoft Support.
If you're still having issues with activating Office 2016 for Mac, please contact Microsoft support.