Boot Camp – Fix Not Asking for USB

I bought a new Macbook and i'm trying to install windows on this computer with bootcamp (i added windows to my other macs too without problem) but this app won't gives me the option to choose the usb drive where he downloads the drivers and boot files… why is the first 1 – 2 step gone ? This way if the windows install starts it tells me there is a problem because no boot file is there… why i can't choose the usb ? did apple updated something ? :/ can't find any solutions… any idea ? Thank you