Hey Thunkers,
Apologies for problems that some folks were having with publish. It turns out that Apple does not accept icons that have any transparency / blank spaces in them. Our general recommendation is for app icons to be 192 x 192 px.
Good
Not good
We updated our troubleshooting docs –
Albert
You should definitely add “adaptive icons” for Thunkable X and also an option to export rounded icon for Android because a squared icon on Android would look really bad and not be compliant to Material Design at all (except adaptive icon of course) 
https://developer.android.com/guide/practices/ui_guidelines/icon_design_adaptive.html