Not being able to turn on crossfire

Hi everyone
I am new here and i have a crossfire problem


So to start . i have an Asus Maximus VI Gene Mb with an i5 4670k cpu ,16gb of ddr 3 mem and Hd 7950 and just added another HD 7950 and a crossfire bridge
,i removed the drivers and cleaned the reg, put in the second card  , and connected the bridge , installed the new drivers (17.7.2 and tried also 17.8.1) but i wont get the crossfire option, and then on a limb i tried installing  the old CCC (13.9) drivers and then the crossfire option showed up , but as soon as i install a newer driver , it goes away , so i have no idea what wrong , windows detects  both cards ...... hope anyone here can help me


with thanks