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My ignition switch would, 99 times out of 100, refuse to push down and lock the steering. Virtually useless.
The main reason for this occurring is that there is a small square metal pin that moves out into a hole in the frame at the steering head, and it can become misaligned with the hole that it is supposed to go into.

We are looking in towards the steering head behind the forks.
Here is the hole (in the centre of the photo) that the pin goes into - it is black metal like the rest of the frame.
The pin protrudes from the alloy ignition switch body that you see on the left of the hole.

There are probably numerous ways of fixing this,
involving the complexity of taking apart the ignition and pin & realigning it all.
When you do, there are some screws that have to be
completely replaced, according to the workshop manual.

I couldn't be bothered with the hassle.
What I did was simply look at where the pin was landing
by moving the ignition key towards locking position,
and at the same time moving the steering about to
see where the pin was hitting against the side of the hole.

Once I determined the edge that was the problem I ground the section of metal slightly,
and put a taper on it's edge so that the pin can move into the hole more easily.

Presto... the steering lock works perfectly again.

Then again, if you are serious about your bike not getting stolen you won't rely on this alone!

Note; there may be another way of addressing this problem if your front forks are already slightly out.

First check that your front fork steering alignment is correct with the front wheel. Maybe it is slightly out... if you have bought the bike second hand then maybe it has had some "trauma" that has misaligned the front steering.
This could put the ignition lock pin out.

If you (jack the bike and then) loosen up the four bolts (2 x allen key, top steering plate, 2 x hex nut, bottom plate)
that fasten the steering head yolks to the forks (there is 2 on either side)
then loosen the four outer (larger) allen key bolts on the fork brace/front wheel guard,
then the whole front steering section is loose and you can move it around marginally
(i.e., change the relationship between where the bars are pointing and where the front wheel is pointing)
--kind of like how you would adjust a push bikes handlebars to the front wheel.

The top alloy steering head plate that carries the ignition switch holds the whole locking mechanism,
and with a slight adjustment of the whole steering it may bring the pin into alignment with the hole.
But you have to keep an eye on the front wheel and that everything else is aligned too; a bit of trial and error.
Make sure you correctly torque all of the bolts when everything, including the pin, is re-aligned.