Not a HP one by any chance? My mother is on her fourth one now.
She had got the first one a few years back and it failed within about 3 months, returned for repair.
The replacement was good for about 12months before the same happened(keys in a diagonal line across the centre of keyboard stop responding or only work occasionally).
Googled it and seems to be a common fault (that HP wont admit to) the fix on that model was to removed the keyboard and the ribbon tape underneath needs folding in a different place and retaping down to stop it moving.
Twas good for about another 12 months , then she decided to replace it with another newer HP model, that failed after a week! screen would only work in certain positions (Back light would cut off when opened fully) Thats been returned and the replacement so far is good.
Seems the keyboards failing and display backlight failing are fairly common and both are generally down to poorly placed/routed wiring at manufacture.