If you've got an Apple Bluetooth Keyboard it may be working fine then one day it just seems to stop working (in a variety of ways such as; the caps/shift lock light not coming on, certain keys working (like alphanumeric) whilst others do (e.g. arrows keys)). So you search the Internet for 'Apple keyboard reset' or 'Apple keyboard fix problem' etc. There's a bunch of pages out there suggesting to just take out the batteries on the keyboard and then put then back in and reconnect the keyboard over Bluetooth.
But it can also be caused by [temporary] software issues on your computer (with the Bluetooth drivers) - so try rebooting your machine (or iPad etc) and try again. It may well fix the problem - as the lack of a caps lock light etc isn't necessarily due to the keyboard itself.