When using Geometry Maps with reference files, a hatch patern Cell was created in a cell library within the dataset. In the Advanced Material editor this pattern is assigned to a material as a Geometry Map. The settings were copied to the library, the material palate was saved and the local copy was removed.This material was then assigned to a Part in the Dataset Explorer.Initially, the objects assigned to the Part appeared with the pattern being displayed, but when a file was referenced into other files, the pattern doesn’t display. When the material was checked, it still had the correct pattern assigned but the path to the pattern file appears to be lost.I’ve noticed this doesn't happen with the brick patterns which seem to load Brick_AU pattern without a problem.
The Cell was lost in the material of the Geometry Map because it was only saved locally and not saved back to the library. There is an option to save to library in the Material Editor.