Mining Rig doesn't See r9 290 between all RX470 Nitro

[Vaperdude]

Good day fellow miners ..

I got a working 3 card mining rig with RX 470 Nitro.
Now i wanted to add a R9 290 4GB but the system doesn't see the R9.

Can anybody tell me what i do wrong?
Driver problem?

Please help.

[OgNasty]

What OS? Are you using risers? Have you checked the PSU cables to make sure they're providing juice? Does it light up with spinning fans or just sit dead? Will it work in another slot? Pictures?

Help us help you.