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. If you purchased Office 2016 for Mac as a single license, you only get a one-time install.