I replied inline
* Is it the .basex file which is located in "C:\Program Files (x86)\BaseX" ?
No, it's located in C:\Users\user.basex
- What happens if you start the start menu shortcut "BaseX Server (Start)"?
C:/Program Files (x86)/BaseX/.basex: writing new configuration file. HTTP Server was started (port: 8984)
Now it works fine