This mockup uses Diplacement Photoshop filter. 

Unfortunately, Photoshop can be a really, really stupid about this:)

That's why, before you will start editing and customizing this mockup, you need to tell Photoshop where the displacement file is, in the first place.

To do that:
- open PSD file
- find Smart Object layer that uses Smart Filters with Displace filter
  (Mockup > Design > Flag layer)
- expand if necessary to show all the Smart Filters
- double click on Displace
- confrim setting with OK button
- then Photoshop will ask you to open displacement file - just choose proper displacement (for example "Displacement.psd") file

Thats it. Sorry for such a mess, but any complains should be mailed to Adobe:-)

Enjoy!
Andrew from mockups-design.com