PCIe SATA card with Proxmox

I'm making a homeserver with Proxmox and I have 10 HDDs connected to a PCIe SATA card, which is connected to the motherboard, however there are issues. Not all disks are detected, and it's really random how many of them are detected and if their format is recognized. The 10 disks are put in 2 racks of 5 each. The 10 disks and 2 fans are powered through an external PSU that I turn on before starting the PC (the PSU is started by making contact between the 15th and 16th pin of the 24 pin connector). All 10 li