Xperia won't enter in flash mode, help needed

Device can enter in fastboot but not in flash mode.
Drivers are correctly installed, (verified by flashing my brothers m2 aqua.)
Device driver shows SEMC FLASH DEVICE. (QHSUSB_BULK)
The green led glow 0.5 second only when entering flash mode.
Flash tool recognised as device connected in debugging off.
I can't flash my Xperia c3 dual.
Please help me guys