no cross fire option

  I just bought 3 RX480 STRIX cards but only 1 is running my monitors. I can see all three in my CCC and GPU Tweak. it shows Cross fire is off but I have no option to turn it back on. I can move my monitors to any of the 3 and each works fine. in GPU Tweak I can see the card that has the monitors hook to it run normal and the remaining 2 have no activity. I have removed the drivers with DDU several times, ive run old drivers. and either I get errors or they do the same. at this moment I went back tot he current driver update 17.2 and get the 1603 Error. I just want my cross fire back please help.