ExternalApplicationExecption

[leaguecn]

hi, dev guys, when i try to export my test model using this tool in Revit 2020, some issues show up, the exception msg as following:

执行外部命令时命令失败
Revit 无法完成外部命令，请与供应商联系以获取帮助，供应商提供给 Revit 的身份信息为: The Building Coder,[ http://thebuildingcoder.typepad.com]

Revit遇到Autodesk.Revit.Exceptions.ExternalApplicationException:未将对象引用设置到对象的实例。
在Autodesk.Revit.DB.CustomExporter.Export(View3D view)
在RvtVa3c.Command.ExportView3DIView3D view3d. String filename)在RvtVa3c.Command.Execute(ExternalCommandData commandData String& message, ElementSet elements)
在apiManagedExecuteCommand(AString*assemblyName,AString* cassName,AString* vendorDescription, MFCApp* pMFCApp, DBView pDBView, AString* message,
Set<Elementid.std:less<Elementid>\tnallc<Elementld>>*ids
Map<AString\AStringstd::less<AString>tnallc<std:pair<AString const AString> > >* data, AString* exceptionName, AString exceptionMessage)

Anyone had the same problem, so what are your tricks to fix it? plz tell me, thx a lot!