The solution is:

1) Start the task manager of Windows, check whether there is a LUM.exe process, and if there is, stop it.

2) Check the files in the specified directory and delete them. Different operating systems and CAD versions may be located in different locations:

win XP:C:\ Documents and Settings \ All Users \ Application Data \ FLEXnet

vista、win7、win8: C:\ProgramData\FLEXnet

CAD2004 or 2006: c: \ documents and settings \ all users \ application data \ Autodesk \ software licenses or c: \ program data \ Autodesk \ software licenses \

CAD2002: under the C_dilla directory (find it yourself)

After finding this directory, delete all the files under it.

3) After the above actions are completed, the error problem has been solved. However, due to the deletion of the activated license file, all CAD software of the automatic workbench must be reactivated. Please find your own way to reactivate, so I won't talk about it here.