Usually the reason is the raisers or a powercable missing…
Is the Raisers properly pressed down in the PCI-E slots?
Is the cables attached properly to the Raiser cards?
Is it connected a power cable to the Raiser card?
If it connected power to the display card?
Has both PSU’s power? And is on?
If you boot into windows. Will the GPU’s appear there? If not it is a hardware connection problem. If not it is a software issue.
When starting HiveOs. Command line screen. Is there no GPU’s listed there?
Is it empty? If so then HiveOs does not detect GPU… If it does, it is a setup with the Miner.
If miner setup, check it has a valid and running flightpath. Then check the miner logs what happend.
Some miners ignorr the cards not compatible. So verify the miner works with your GPU… Or it will not detect the GPU…