Biostar tb 250-btc pro

I am using BIOSTAR TB 250-BTC PRO.
So far, I have made 10 12GPURIG with GTX1070.Everything is working fine.

This time, I tried to configure a 12 GPU RIG using AMD RX5700XT.
However, although it starts up to 10 GPUs, when the 11th is connected, the BIOS is not displayed.

I also changed the connection order and cables.
I tried replacing M / B, CPU, MEM, PSU, GPU, riser card, etc., but the status does not change.

No matter what I do, when I connect the 11th sheet, the screen does not appear, and there is no signal on the monitor.

Is there a BIOS setting for AMD or RX5700XT?

This is my first experience and I am in great trouble. Please give me some good advice.

I look forward to working with you.