I'm working on three Precision M3800s having the same issue that all need board swaps. I've replaced the first two, and with both, I haven't gotten the usual prompt to set the service tag when I first boot it up, and the service tag field in the BIOS says (None).
I've talked to a couple of people in Dell support and was told to use CCTK to update the asset tag, which I did, and it worked, but it didn't affect the service tag. I was then told that it meant the BIOS must be corrupt and I'd need to replace the board again. Then when I installed the second laptop's board and had the exact same issue, I was instructed to enter the service tag in the BIOS, but it isn't an editable field.
I'm at a loss here. I've seen a couple of posts saying I should update the BIOS, but there is no BIOS update download on the driver support page. Has anyone else had this problem?