Are you saying you can't get an external one to work with the tablet? If that is the case, did you make sure that the keyboard you are using actually works with your tablet? Unlike with computers, not all keyboards work with all tablets.
If this isn't a keyboard you bought separately, but one that actually came with the tablet (or is one that works with your tablet for sure), how to fix it is going to depend on what the actual problem is.
Is it registering anything you touch on the keyboard? Or nothing at all. If it is registering some things/keys, but not others, you may way have gotten something in the keyboard and would need to see about cleaning it out. If it isn't registering at all there are a couple things you could try. If...