Connect an external USB keyboard and try that for a while. If the issue also occurs with the external keyboard, then the issue is something in Windows or driver. If the issue does not occur with the external keyboard, then it's a hardware issue with the onboard keyboard.

I'm unable to determine if that model uses a battery for the keyboard. Can you use the keyboard without a physical connection to the tablet? If so, then there must be a battery. If not, if it must always be connected to the tablet to work, then there may not be a battery as it may receive power from the tablet.

You can also look here: https://www.dell.com/support/kbdoc/en-ca/000131432/keyboard-usage-and-troubleshooting-guide

The keyboard is not BT or USB connector, it seems to be made for this specific labtop model as I can see the pins are specific for this one.  I am pretty sure is not the driver or windows issues.  Right now, the only way to access bios is use the volume button as keyboard does not even work.

https://www.ebay.com/itm/304607068592

I am not so sure what you are asking me to do, the reason I'm saying it's not related to windows is before this issue occur, when the labtop boot-up, I am able to use the keyboard to trigger the Bios menu.  Now I am not so this is why I don't think it's related to windows as the hardware should work before even windows kick in right?  If the issue is Windows then it should only failed when windows is loaded, my case it's not.

connecting to external USB keyboard seems to be working fine.  I've even bought another set of keyboard Dell Latitude 12 K14M Slim Tablet Base Keyboards which also failed to work so I suspect the issue is with the hardware not detecting the proprietary Dell keyboard.