App icon not showing on all devices.

I have just uploaded a new version of my app to the Google Play store, but the App Icon isn't showing up on some devices (so far the only report is from a Pixel 2 user.. who is my boss' brother so she's personally invested in getting this resolved)

When I download the app on my phone it looks fine - but on the screenshot provided to me it is showing the default Unity icon instead.

Is there a reason this would work on some devices and not others? Searching this problem I'm vaguely aware that it may be a Manifest issue - but I've never had to deal with the Manifest before (this isn't the first version of the App we've released) so I have no idea where to begin. I'm getting conflicting answers as to where the manifest is and whether Unity takes care of this or whether I have to use Android Studio (which I don't know the first thing about) that I suspect are due to different versions of Unity

The project was built in 2018.2.0b3 - I needed this version for the fix to Android movies in Assetbundles but moving out of the beta build breaks my prefabs, so I'm kind of stuck on it.

The app is called Augle - so if others are willing to download it just so I can get a broader picture of how many devices are affected that would be great too.

 

This answered my question;
https://forum.unity.com/threads/android-oreo-icon-is-incorrect-on-unity-5-5-0p4.492300/

I see the adaptive and round icons in the editor - I'm a little irked that the 'default icon' didn't automatically get copied over into these.