Exporting image as PNG shows blank

I usually export all files as PNG to share easier through email, text or other messaging services.  I am not unable to export as "png" as it just shows a blank area when previewing what the PNG will look like.  Does not matter if the background is white, black or transparent it shows nothing as if there isn't an image being exported.  Please offere any advice if you've had this happen or simple troubleshooting that i can use to try to fix this.