This problem may due to several reasons, let’s check the problem by following steps.
Possible cause 1:
The version of the drawing file may be higher than the version of the ZWCAD program you are using. For example, if you use ZWCAD 2009 to open a drawing file whose format is AutoCAD 2010, then you will get message illustrated below: “Error: I. Unable to open the requested file. Only drawing version 2.5 and higher are supported.”
Open the drawing with the latest version of ZWCAD.
Possible cause 2:
The name of the file conflicts with the regional language of the Windows operation system. Generally ZWCAD is compatible with most language but for some special situation, it may be the reason.
Rename the file with number or English. After it is solved by this, please report this problem to ZWCAD Technical Support Team (Go to Service & Support > Product Support > Technical Support). Please provide your files name and the language and regional option of your operation system. Thank you for your help to make ZWCAD better and better.
Possible cause 3:
The drawing may be damaged.
Solution: Try to use ZWCAD to repair the drawing.
(1) Audit command:
From ZWCAD’s File menu, choose Drawing Utilities, and then Audit
This command reads the drawing file, and then provides a report on the state of the file, such as whether errors exist in the file’s content.
(2) Recover command:
From ZWCAD’s File menu, choose Drawing Utilities, and then Recover. This command recovers damaged drawing files in DWG format only; DXF files can be recovering only after they are opened.
Possible cause 4:
If you get this problem when open the drawing by double-click the drawing, it may due to the manner in which Windows registers file extensions.
Instead of double-clicking the file to open it, try opening it through ZWCAD’s File menu: select Open, if the problem occurs only when you double-click the file name