
Facebook in its blog post, has announced that it is phasing out third-party invites. This feature was designed and reserved for games from developers like Zynga and others.
The social network has been allowing its users to invite other users to become players.
This was a hit back in the days when games like FarmVille and others were popular on the social network. But since then, not that many people are really into them, and many have even blocked app invites from ever showing up on their notification and feeds.
According to Facebook:

Facebook is slowly phasing the feature out. According to the developer page, by February 6, 2018, Facebook will cease support for the feature.
Facebook is also deprecating a few other features at the same time. This includes third-party Like buttons.
What this means, users won't be able to Like a Page while using another app. To Like a page, they need to visit the actual Facebook Page and hit that Like button.
The social media is also deprecating comment mirroring that allows users to comment on offsite contents using their Facebook account, the edge.create and removing JS SDK Events, sunsetting App Links Host, shutting down the Send Button, the Follow button and also the Sharing Insights.