This issue usually happens because BricsCAD’s LISP environment is not 100% identical to AutoCAD’s, and a .FAS file compiled for AutoCAD may contain functions or calls that BricsCAD doesn’t support. Even if the logic is the same, the compiled FAS can be platform-specific. To fix this, try compiling the LISP separately for BricsCAD using its own vlisp or compile tools, or load the original .LSP file in BricsCAD to confirm it works before compiling. Also make sure the file path is trusted in Settings → Program Options → Files → Trusted Locations, as BricsCAD blocks untrusted FAS files by default.