The problem I found with mine is no amount of wd40 or similar would help as lock was physically jammed as grit had got past seal ring.
I ended up after a few years taking the lock apart again to clean it out but this time replaced the internal seal in the housing holding the push button and replaced this with a felt seal, not had a problem since, that was around 2 years ago, prior to that I was doing the lock between 2 and 3 times a year, take out strip down clean out etc etc.
My mate pissed himself laughing as I carried a block of 6x2 around to open the lock, but carried it in the boot ha ha, what a numpty!!
tabetha