You are right. It works if I use the windows shortcut on the desktop.
In fact I had forgotten that I was using a keyboard shortcut to launch MusicBEE with a .BAT file
I just changed it :
@echo off
cd "C:\Program Files (x86)\MusicBee\"
REM start MusicBee.exe /play /next
start MusicBee.exe
Thank you very much for your help.
Regards
Philippe