To use the Lumion 8.5 Material Library, you'll need to have the following:

Run Lumion as Administrator. If the crash persists, you likely have a corrupted third-party material. Delete the most recently added texture from your Documents/Lumion/Library folder.

The most reliable method for obtaining the complete, pre-configured material library (which includes over 1,468 textures for Lumion 8.5) is through official channels: Free Trial Try Lumion Pro for 14 Days

He needed better materials. Specifically, he needed the high-resolution, physically-based rendering (PBR) assets that were part of the expanded material libraries he saw online. His version of Lumion 8.5 had the standard catalog, but it wasn't cutting it for a project of this scale.

Searching for a "Lumion 8.5 Material Library free download" often leads to torrent sites or cracked repositories. While it is technically possible to find these files, downloading them comes with severe risks: