The reason why Discussions feature is not available for your Page could be that, you might have chosen a Package for your Page for which the Discussions App is not available. In this case, you can see if choosing a different Package with the Discussions App suits you. You can change the Package for your Page from the “Packages” section of your Page Dashboard.
Availability of Packages for Pages, and their features are conditional depending on the settings chosen by our site administrator.