You mean that the texture images used in making the materials is not found.
Unless the images are in a folder LOADED INTO THE ARCHICAD LIBRARY, they will not be available.
So, you'll find these materials wherever you left them last, to use my mother's admonition about missing socks.
To make them accessible, place them in a folder and use the Library manager to add that folder to the folders used as the Library. They can be anywhere.
Dwight Atkinson