I also tried exporting without alpha it did not work for me but I figured it out that why I was getting error. I create an AppIcon using Figma & Sketch, but I tried to make a 2D geometry shape to 3D viewable. So I assume that I can achieve it by using some shadows & the same geometry but with lower alpha-like %70. After that, I got the AppIcon and export it without Alpha ticking but the problem was the main source of the image includes a container with lower alpha-like I did. So I change it to another graphical shape without alpha and it worked.

将图标从。png格式改为。jpg格式，一切都很顺利。

I also tried exporting without alpha it did not work for me but I figured it out that why I was getting error. I create an AppIcon using Figma & Sketch, but I tried to make a 2D geometry shape to 3D viewable. So I assume that I can achieve it by using some shadows & the same geometry but with lower alpha-like %70. After that, I got the AppIcon and export it without Alpha ticking but the problem was the main source of the image includes a container with lower alpha-like I did. So I change it to another graphical shape without alpha and it worked.

我可以通过复制文件来解决Mac Sierra OS的问题，将新文件拖到桌面上，在预览中打开，然后单击导出选项(在文件菜单中)，然后出现不带“alpha”的保存选项

无效的应用商店图标。在YourApp的资产目录中的应用商店图标。App '不能是透明的，也不能包含alpha通道。

在卡特琳娜解决

复制到桌面 在预览APP中打开图像。 关闭第一个打开的预览 在尝试关闭第二个复制的图像后，它会提示保存在那里，你可以取消勾选AlPHA

看看我的截图

如果ionic3项目在上传到iTunes Connect时显示此错误，请检查此答案

这是我的项目错误，当我试图诋毁。

最后遵循这个答案，错误解决了。