Drivers auxiliary door lock barrel wont turn with key

Hello, this morning key fob died when trying to lock my car, so i went to use the auxiliary lock on the drivers door by popping the cap off, however when i put the key in the barrel just would not turn, i tried a touch of WD40 to see if i would loose it off but nothing, i have never used the auxiliary lock since i got the car so its probably never been used since it left the factory.

anyone came across this or have any suggestions? 

thanks