It might possibly be frozen, you can try with some de-ice product. Something else worth to try : I know there is a special grease for locks (Toyota dealers generally do have some) that work EXTREMELY well : I had the same problem some time ago, the dealer I know put some of that grease and since then I don't have any problem at all with it, it's just like new.
If your stuff was good for garbage I would recommend you to go your dealer so that he could order a new one, corresponding to your key (so that you don't have 5 different keys for your car

)
Good luck !