After a few days with computer on, I restarted it, after that I can no longer make the player appear, I double click on the application icon, but it does not appear in the system tray (because I set it to start minimized there), it does not responds to configured hotkeys, however, the application process stays in the Windows task manager.
I am using Windows 10 x64, Musicbee 3.3.7191.35723.