Just fix your png to really fit this condition and it will work (It worked for me with a transparent png with my logo (only the border in black) and background transparent too).
You can also try to reformat your png with online tool ? (like this one)
I have the same problem. But my app is a bare workflow project. Didn’t found any way to set the notification icon, I’ve already tried manifest config, app.json config, placing icons in different folders (drawable and mipmap folders) and it just doesn’t works.