Hi to everybody.
I bought a Radeon RX Vega 64 8 GB and yesterday I tried to install on mining rig. I must point out that until yesterday 3 RX 580 Sapphire Nitro and 1 Nvidia 1660 TI cards were installed. I removed all the cards and tried to install the VEGA 64, but the system does not see it.

Motherboard is B250 Mining Board BTC 12GPU

Where I was wrong? What do I have to do to make the system to see the card?

Thanks a lot