third monitor off second card

[hewgo]

hey guys iv never done anything like these forums so excuse my in experience but i built my pc a little while ago and i decided to go with three monitors. now i have 2 crossfired asus 7870s and i have the first two on the primary card but if i try and use the second card for the third monitor(i have no more ports on the primary) it just wont happen it almost like nothings plugged in any suggestions?

 

[k1114]

All monitors must be on the first and you have to use active display port adapters for 3+ monitors.