I guess the linked video has been moved (or renamed, deleted etc.).
Me pasa lo mismo!
¿Cómo lo solucionaste?
What version of Photoshop are you using? And, are you on a Mac or Window machine running what OS?
Are you using Smart Objects, and if so, have you moved the original images?
Let us know so we can help you.
Buenas tardes, a mí me ocurre lo mismo
Please read this (in particular the section titled "Supply pertinent information for more timely and effective answers”):