CAD tip # 11145:

Customization file load failed. File not found

or (German):

Laden der Anpassungsdatei fehlgeschlagen. Datei nicht gefunden

and after confirming it, AutoCAD opens without any menu/ribbon.

Either the CUI/CUIX file ACAD.CUIX is missing in the folder (e.g.) C:\Users\USERNAME\AppData\Roaming\Autodesk\AutoCAD 2017\R21.0\enu\Support\ or your user profile is damaged (or AutoCAD runs in an emulated mode, e.g. Citrix). In this case it may be neccessary to re-create the profile or reset it.

In the Windows menu Start, in the AutoCAD folder, click on "Reset settings to default".

If it doesn't help, try to delete the profile information, the secondary installer will later re-create it automatically:

• In the Windows Registry, delete (backup first) the key to your AutoCAD version - e.g. HKEY_CURRENT_USER\SOFTWARE\Autodesk\AutoCAD\R21.0
• Delete (rather rename) the application settings folder - e.g. C:\Users\USERNAME\AppData\Roaming\Autodesk\AutoCAD 2017\R21.0