Verify that the file storage location is working properly.Test opening the file in a different location, such as the local hard disk, to rule out network or cloud storage issues.If you see the error message in conjunction with crashing of AutoCAD products in the Collaboration for Civil 3D workflow, see Desktop Connector shuts down and Civil 3D crashes as a result.Find a backup or auto-save copy of the file (see Understanding backup and autosave files in AutoCAD).If the first few rows are consistently different in format, this indicates irrevocable corruption, improper conversion, or wrong file type. Check the file in a text editor such as Notepad and compare to a known-working drawing.Open files created in non-AutoCAD (third-party) applications in the native product and export to AutoCAD DWG format, if available.Open the drawing file directly instead of using the shortcut in the Recent Documents menu.If the file can be opened anywhere, save it to a previous file format.See: Optimizing drawing files in AutoCAD with Purge, Audit & Recover.
