When external devices like printers, scanners, etc. are connected to a Windows 11/10 system, the device either pushes the drivers through the USB (or any other post), or the user is expected to ...

When this happens, it means that more than one device is trying to use the same I/O port. Open the device manager and see if there are any yellow exclamation points ...

Additional info: rereading the mobo manual, I realized I had plugged the HDs into SATA 3 and 4. When the C: drive is connected to SATA 1 and to SATA 2, the machine doesn't even get as far as the BIOS.