Here’s a quick tip on how to locate your AutoCAD Hatch Patterns and then set the path. The problem may arise when you have multiple installations of AutoCAD you may have more than one. The path to your hatch pattern definitions can be found in the Support folder in AutoCAD. This PAT file is loaded every time you open a drawing in AutoCAD, and is used to set the default hatch patterns available in AutoCAD.
The acad.pat (pattern / hatch) is a text file in AutoCAD that contains the source code for your hatch patterns.