As new mentioned check the dmesg, if those NIC are recognized and visible during bootupI would advice to not only reset the BIOS but to actually inspect what is set in BIOS. The NICs can be by default disabled in BIOS you have to check it out.
If NIC are turned on in BIOS but OPNsense does not recognize them, try to boot up a liveusb of any linux distro and see if they are there. If the above is done and verified and they wont show, its possible those NICs are cooked.
To check if Ports are not disabled they are actually on the PCIe lines, check the input from Beck
Jumpers inside the case to turn them on/off? Is there a BIOS that you can flash, even if the same version?