I've recently bought myself a new mountain bike (my first since my schooldays...) and it has front suspension with a lock-out function. Suspension is new to me and I'm not sure how to use the lock-out. It seems I have to stop and take my weight off the bike to lock-out the suspension - is this correct? Or should I be able to operate the lock-out whilst sat on the bike and I'm just not turning the lock-out hard enough? As I'm not really sure, I've avoided turning it too hard in case I do some damage.
Less expensive forks have a mechanical lockout. This type of lockout is only usable when the fork is unweighted. Think of it like trying to deadbolt your door when it's still ajar.
With an inexpensive coil sprung fork the lock out is often only usable with no weight on the fork. So yours is probably working normally.
Lockouts are most useful for sprinting and climbing, when your weight moves forwards and your putting in more effort that you don't want to waste.
More importantly, don't forget to free it again if you get enar anything bumpy, you can damage a fork like that.
(Personally, even with a remote lockout I rarely use it, except on perfectly smooth tarmac.)