Replacement keyboard not working

My “P” key stopped working on my Dell Precision M4800. I ordered THREE different replacement keyboards, one with exact same part numbers. None of the replacement kbds show up in BIOS or device mgr (as PS2). If I put the original kbd back in. It works and shows up in BIOS and device manager. Could the firmware be linked to a specific serial number? That would be rather stupid. Any ideas?