My rig used to have 2 RTX 3060, 1 GTX 1660 super and a AMD RX 580 8GB. I bought 4 RTX 3060 and a 500w power source to add to my rig.
After the install, I boot it up and it shows sometimes one or to gpus as missing unit. And the other doesn’t start mining.
After a minute or so the rig goes offline. I check the connection in other devices and it’s ok.
In my rig dashboard on HiveOS it apears in red in the right top corner “LA” and some numbers after it. that are not the same all the time. “LA” stands for “High load average”. But when i just disconnect USB from the risers and leave one to test, it goes perfectly.
The symptoms as described are nearly always low level interactions with Motherboard, PCI detection, Risers, Cables, etc.
Errors in OS detection would be due to drivers, recognition of new release GPUs(Chipsets requiring new drivers), etc.
There is a not enough information provided to assist in either case, but the first example and the impact of “disconnect of USB” is evidence of the first group of troubleshooting suggestions.