desert marten
When Photoshop is running, from the main menu go to: Edit > Preferences > General... Click on "Reset Preferences On Quit" and then close (and reopen) Photoshop. The preferences will be reset.
If Photoshop is not running, press and hold Ctrl + Alt + Shift (on Windows) or Command + Option + Shift (on MacOS) while you launch Photoshop. You should see a message asking if you want to delete the Photoshop settings file. Click 'Yes' and the preferences will be reset during startup.
For more information about Photoshop Preferences, see the following page: https://helpx.adobe.com/photoshop/using/preferences.html
...
