lsing png file's transparent bacgkround during photomerge

Good afternoon,

I'm trying to add my logo to a graphic. My logo file is a png file with the needed checkerboard (transparent) background.

As soon as I use the photomerge process to place my logo on my graphic, the logo file loses its checkerboard (re transparent) background, switching to white. I've attempted different formats for the graphic on which my logo will be placed -- in case that made a difference -- but to no avail.

Thank you,

Martin