Earlier this year, Google decided to stop investing in Allo and pushed some of its popular features — such as Smart Reply, GIFs, and desktop support — to the Messages app. Yesterday, Google has finally confirmed that the smart messaging app Allo will go down, but it will continue to work until March 2019.
https://www.notebookcheck.net/Google-has-decided-to-stop-supporting-Allo-and-focus-on-Messages-instead.374681.0.html