After several plug was installed in Niksoftware of Photoshop CS6, the window was not displayed with Selective Tool. The menu item File / Automate the start of Selective Tool is missing.
Have you checked with Nik for updates?
Have you checked Help->System Info to see if the selective tool plugin is recognized at all or not being loaded for some reason?
The latest updates are installed and in the diretory "Plug-Ins\Nik Software\Selective Tool" there are Dfine2.config, SelectivePalette.8li.
In Help->System under Optionale Zusatzmodule und Zusatzmodule von Drittanbietern there are
Color Efex Pro, Dfine, Sharpener Pro and Viveza but not Selective Tool
Alright, that rules out the easy stuff.
At this point you need to talk to Nik and see if they know what is going on with their plugin.
Ich habe das gleiche Problem seit heute. Konntest du das lösen?