If when you try to paint, nothing is visible:
- Check the current selected colour at the bottom right and make sure that it’s not set to white.
- If you are using your finger, if you have previously set the app to use only a stylus, this could be the cause. Check your stylus preferences.
If when you try to paint, you see an eye icon appear, this indicates that the layer you are trying to paint on is hidden. Open the layer panel, and for the currently selected layer which is shown with a green highlight, tap the closed eye icon. This will show the layer contents and allow you to paint.