Mac will not shut down/sleep

So I spilled some water on my MacBook keyboard a couple of days ago and after drying it everything works fine now except for the keyboard, now using a USB keyboard.

It strangely won't shut down or sleep. If I press the shut down button it goes through the process and the screen goes black, but, then it boots right up again. Similarly, if I select sleep the screen starts going black, but, then it comes right back on. And if I close the lid the screen goes black, but, I can still hear the fan etc... running.

Any advice as this is totally impractical to use. I know the computer is old but it seems a shame because everything else works perfectly :(

Any advice on what is happening would be greatly appreciated!