Can't make Explorer-like interface the default

I have the feeling that I'm missing something obvious.

I select option to use the explorer-type interface and then I immediately go to "stored sessions" and click on "set defaults". I close the program and when I restart it, the Norton Commander interface is default again.

Can someone tell me what I'm doing wrong?

"Set defaults" affect only session settings. Interface selection is global setting.

Your interface selection is stored only if you actually utilize it (when you open session and the main window with it). If you press "Close", it is lost.