The warning message "No valid Tuning file specified, the default import tuning will be used. It will put each attribute in a new layer" appears and the file is blank, the design is not available in any of the layers.
The user interface doesn't show the preview of the DXF file.
Warning message may appear after upgrading to ArtiosCAD 12.1.1, check the tuning tables in the Shareddefaults, could have been using the old version of the Tuning Table. Examples of old and updated Import Tuning Table:
Replace the old Tuning Table with the new ones, both Inch and Metric. The latest ArtiosCAD System defaults will be available in C:\Esko\Artios\ArtiosCAD12.1.1en\InstLib\sysdflt.adf.
Open Defaults, go to Options menu > click Defaults > and in the flyout menu expand Import Tuning Table.
Click the User defaults panel ( the User defaults radio button gets highlighted).
Go to File menu > Open > click File... > browse to C:\Esko\Artios\ArtiosCAD12.1.1en\InstLib. Select sysdflt.adf and click the Open button.
The default settings are visible on the User defaults panel, select and expand Import Tuning Table > select Artios DWG/DXF - Inch, drag and drop into Artios folder under the Import Tuning Table in the Shared defaults panel, similarly drag and drop the Artios DWG/DXF - Metric.