Help! My image won't export properly

[Megan29972580rksb]

I export the image but the download doesn't look the same as it does on the app. It has multiple layers but I did the exact same thing with the icon and it downloaded as it's supposed to look. But the banner does not! I tried both export options and look how differentit is. Yet the icon exported fine. ????? This is driving me crazy!

[lambiloon]

Hi try to make sure what is your artboard size,  problem is there I think...regards

[Megan29972580rksb]

Thank you, but I don't understand--what is artboard size? And why does that effect the way the image looks when exported?