I don't know if it's a bios issue, or that the cards are incompatible with the riser.
When I boot the server, the fans boot up, lights start flashing, but the OS doesn't boot and nothing (no bios GUI) comes on the monitor. Monitor stays turned off. There is one red light that flashes. The power button lights up green (good).
The server did not originally come with this riser card. It came with a PCI Express riser card and I swapped it out. The server boots with the riser card as long as there is no PCI card installed.