Why does PNG not display as transparent?

[LondonPhotographer]

When I move a png file on top of a jpg file it still seems to display its checkerboard background. I have double-checked that it is a proper png file by re-exporting with transparency checked. But still no dice. Not sure what I'm doing wrong. Example below. Thanks.

[c.pfaffenbichler]

Please post the png. 

Please post a meaningful screenshot that includes the pertinent UI elements (Options Bar, Toolbar, Layers Panel, Channels Panel, …),