Is this a desktop?

If it's a desktop, keyboards aren't that expensive. You can probly find one on ebay for ten bucks American. If it's a laptop, it still might could be fixed. But it's more complicated. In other words, not for the faint of heart.

What happened between now and the last time it was working properly?

Is it possible that you got some food crumbs or liquid into the KB?

How old is the device?

I second the idea to turn it upside down and (gently!) shake it, in case something you don't know about might have gotten into it.

I can't imagine how the operating system could have caused it. But I guess anything is possible.

Best o luck!

Saul