Please start AutoCAD then type CUI on the command line so that Customize User Interface dialog box is displayed. In the top left section, expand the Partial Customization Files and check if AutoTURN is on the list and if it is marked as Unresolved.
If you have AutoTURN on the list and it is marked as Unresolved, please right click on it and unload it. Click on OK to close CUI dialog box and then close AutoCAD. Use AutoTURN desktop shortcut to start it in AutoCAD and confirm that now the AutoTURN toolbar or ribbon is displayed.