RX580 - no GPU units

Hi all,

I’m new to gpu mining and I have some problems using both Nvidia and AMD cards. The AMD card is connected through a 1x to 16x riser. Sometimes both cards are working but sometimes HiveOS cannot detect the AMD card.

My system is:
MoBo : ASUS TUF B360M-PLUS GAMING
CPU : Intel i5-9400F
GPU : Nvidia 1660 ti & AMD RX580 8G
Coin : ETH
Miner: pheonix miner
HiveOS ver: 0.6-203@210403

Is the problem from the riser or should I lower the OC frequency?
Any suggestion would be appreciated.