Are you sure that Crossfire works between a R9 Nano and a R9 290 card?
When I look at the Crossfire compatibility chart at AMD CrossFire™ Compatibility Chart, few cards work with cards from other series. Normally you want to match your primary card with your secondary so you have cards from the same family + model in all slots. The compatibility chart I found does not include the newest cards (R9 Nano/Fury/Fury X), but the basic principle is probably the same.
It may very well be so that DirectX12/Vulcan will allow compatibility between more different cards if the developers put in the work (like for example the Ashes of the Singularity developers have demonstrated), but for now with DirectX 9/10/11-software you are probably restricted to the compatibility matrix stuff.
Those graphics cards are not compatible. The R9 Nano is compatible with the Fury X/Fury/Nano.
Thx for the quick response. Well the incompatibility explaines the missing option .Than i go ahead and sell the 290 as i had planned anyway^^