Function keys don't work anymore - Logitech Cordless Desktop MX 3000 Keyboard/Mouse

Maybe u should buy a new one or go back to the store and ask for help.

Have you don a OS upgrade? Any updates? Try HP support: http://h10025.www1.hp.com/ewfrf/wc/documentSubCategory?tmp_rule=44083&tmp_task=solveCategory&cc=us&dlc=en&lc=en&product=4230715

You have activated the number lock on your laptop to unlock press the "fn" function key and 'NumLk" key that should get it back to normal

Replace the keyboard, they are not made to be serviced,

Change the battery in the remote.

It's called 'The seven year itch', just a year late. You just don't ring your car's chimes anymore.

Locate the Blue Function key, generally denoted (fn) You need to hold this key while press a key with blue functionality for it to work.

Comment if you need further assistance

Sometimes keys get stuck and sometimes the contacts don't work anymore. Carefully turn the laptop over and gently tap it on the back to knock out any grit that might be under the key. You can also carefully use a soft paint brush to see if there's any hair, dirt or grit around the key that is preventing contact. You can also try canned air to spray out dust. If you have a pet it's quite common to get fur in the keyboard even when the cat or dog isn't near it :)

Keys on laptops don't come off and go back on as easily as they do on normal keyboards so removing the key might get you into a fix...ie break it. So I wouldn't recommend trying that if you're not familar with how it connects.

It could be that the mechanism has worn out in which case you'll have to replace the keyboard itself.

That's because you activated the NumLock mode!
Have a look at your keyboard -upper right-, you'll find a "NumLock" key, push it once more and you will deactivate it and retrieve the normal use of any keys!
Good luck, Jopica123