I have a PNG with a transparent background, however the checkboard background does not disppear when imported into another document. Having had a look around for a solution I see it's been going on for at least five years without being fixed.
1. Are you absolutely sure your png has transparency and has not been downloaded with a solid checkerboard layer? It is a common issue for example using images downloaded from websites where the preview has been downloaded rather than the actual image with transparency.
2. How are you using it within another document?
From memory, the issue has been that there is actually a checkerboard pattern with no transparency in some files from stock photo sites.
Can you provide the file or even a cropped section that contains both opaque and transparent pixels?
That's normal behavior. You need to open the .eps image in Illustrator or other vector application and turn off or delete the layer with the checkerboard.
JPEG doesn't support transparency. Save it as PNG including transparency, is the transparency retained? As previously mentioned by Jane and myself, some files include the background. A vector file should be edited in a vector app.
It seems the file I was having issues with was indeed an image on a transparent layer, only PS did not handle it as expected. I managed to extract the image from the checkboard background from a Photoshop PDF. It had broken the illustration down into its component pieces as layers in group and design folders, which I flattened to get the illustration.