A family of Microsoft word processing software products for creating web, email, and print documents.
It is also possible that this is one of the features not available for the perpetual Office 2016 license. You have the perpetual license version, not the subscription version of Office.
It may have been available earlier because sometimes Microsoft makes mistakes in their distribution of update code. The subscription version and the perpetual license version are related and share most of their code. When updates go out, sometimes a subscription feature is included in the perpetual license update and then they discover their mistake. In another update, they remove that feature from the perpetual license version.
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The idea of the subscription version is that when new features are added to Office, they go out to the subscribers. The perpetual license version is fixed at the features you purchase when it is released. Updates in perpetual license versions are for bug fixes and security, but not for features.
You could subscribe if you wish to change, but there is no credit for the perpetual license.