Yes, full specs would help. Or post a link to your PCPartPicker list so we can see it all.
This is rarely a problem if you know about it. As a GENERAL explanation, this may help. SSD's first came out in cases set to fit into common mounting places for SATA HDD's, and using SATA connectors and SATA HDD simulators inside. So you just plugged them in like a SATA HDD, but they were MUCH faster. Then came a different form on a small circuit board that fit into a dedicated new slot type on the mobo, but these were still made to operate like a SATA HDD only connected directly to the PCIe bus, and hence faster yet. And the latest scheme is an almost identical circuit board appearance, but internally connected to that same PCIe bus in a different way, and these are called NVMe SSD's, even faster. Moreover, the type of RAM units inside these latest are super-fast. Mobos that accept these NVMe-type SSD units also often can accept the earlier ones that looked the same, but operated more like really fast SATA drives. So these mobos are set up so that, IF the unit you mount in that special socket is the simulated-SATA type, not the newest NVMe type, then it treats that unit as using one of the existing real SATA ports on your mobo. Thus that one real SATA port (the mobo manual will tell you which one) is not available for something else. BUT your mobo also will have three or five (or more) MORE real SATA ports you CAN use. So, if that is your situation, you simply do NOT try to use that one SATA port, and leave it alone for the SSD unit in the special socket. Just connect your real SATA units to any other ports.