if I rightclick on the icon of ssc and click more, I get the option 'run as administrator', so I think that I did not run it as administrator before.
None of the standard hotkeys function. If I customize some of the hotkeys, they do work. I can now capture a selected region with Ctrl + Q and the active window with Ctrl + W. Thank you for your help. This has solved my problem.

I have installed Screenshot Captor and it automatically starts with windows. I want it to stay minimized, which is does. But the shortcut keys don't work. I have to make Screenshot Captor visible on the screen and navigate to Capture, grab selected region to be able to make a screenshot. How can I make the shortcuts working so that I can make a partial screenshot, just by typing Shift+PtrScr, even when the window of Screenshot Captor is not visible?