Where is the PSD file?
If you downloaded a mockup from this site and expected to find a PSD file after unzipping the archive please note there is no PSD file.
The only file in the download is an Action file (ends with .atn). An Action file is a script that can be executed from within Photoshop which generates special effects, creates new documents, can batch process a series of images and so on.
The case of PSDCovers Actions, our actions generate the entire product shot mockup and presents it to you as a multi-layered document which you can then save on your computer.