Thanks for writing to us.
As both the old and the new keyboards are not working, looks like the port on the motherboard is gone faulty.
Just to doublecheck you can try an external USB keyboard and check how its working.
If the system is under warranty, Please click my DELL-username and write me a private
conversation with the service tag and your contact details(Name, Phone#, Address and Email). We will see what best option we have got. If
there is no warranty, then you could contact our team to get a quote for a paid service call -
in blue and then select send a private message