Lock the steering - VZ800

Hi, I'm a newbie in the forum and riding bikes, just recently acquired my first bike, and it's a VZ800 - 1999.
Just got one question. I've got two keys, one for starting the bike/open gas, and other for locking the steering.
I've tried to lock the steering, but I can't. I'm assuming the process is turning the steering full left, and then turn the key counter-clock wise, and it should be locked, but I can only turn the key slightly (1/4 turn), it doesn't go all the way.
Is there any trick to lock it that I'm missing ?
Is it broken, and that is the reason why I can't lock it ?
Thanks.