QB-35RFE FireWire 800 don't work!

    QB-35RFE FireWire 800 don't work!

    Hi,
    I used for many years the QB-35RFE with the USB cable.
    Now I've connected it with a FireWire card that have both connector for 400 and 800.
    If I connect the QB-35RFE to the 400 connector it works fine but when I connect the QB-35RFE to the 800 connector it don't works! Why?!
    It's also impossible to power on the QB-35RFE when the 800 cable is connected. I've tried with different 800 cables and with two different FireWire card but nothing is changed!

    I need to use my QB-35RFE with the full speed of the 800 Firewire connection!
    I'm using Win10 Home, Mother Board ASUS PRIME X370-PRO with AMD Ryzen 7 1800x - 16Gb. DDR4.

    Thanks for support.
    Davide.