Launcher Icon is not Shown in Oreo 8.0/8.1

Explanation:

I have a working app in google play market. Everything works fine in android versions from 4.0-7.0.

Case:

When the client downloaded it on his Android 8.0 (Oreo) a launcher icon did not seem to show instead android's default launcher icon is showing!!

Question:

Anyone who has encountered such issue? I need any hints to solve it since it seems weird because I have all 4 typed .png icons in mipmap folder.

Where is my launcher icon?

See also. A Launcher icon is a graphic that represents your application on the device's Home screen and in the Launcher window. The user opens the Launcher by touching the icon at the bottom of the Home screen. The Launcher opens and exposes the icons for all of the installed applications.

Yes, I also faced the same issue in Android Oreo.