I pressed the little button to pop the trunk on my KJ Series 2 and the horn started going off.

Anyway, now when I press the red button the horn beeps twice but it doesn't lock.
I lock the car with the key and the green button unlocks it.

What should I do to fix this?

Thanks

Have you made sure the boot is closed properly or any doors left ajar?
Thats what the double beep is telling you.
With the boot release, press it once then again and it should pop without the horn going off. Holding it down sets the panic alarm off.

If I were you, Id probably end up disconnecting the battery. Though it would be a wild stab.
I did have mine go a bit crazy on me (wouldnt stop suggesting Ive left a door open) after checking all the doors a billion times. A short drive and then it decided to work...
I wrote this assuming you knew what the beeping was for and had checked all the doors of course! :)

the vrx does a double beep when a door is left open.this may be your problem as stated earlier

It also happen to me once, i found out I was not closed the boot lid properly. After I slam closed the boot, the alarm behave normal.

Funnily enough, I just accessed my boot and closed it. I went to lock the car and it beeped at me. Opening it again and re-closing it worked. This has only ever happened to me once before, so odd timing! Starting to wonder if maybe there are common problems with the lock not being registered as closed.

Thanks guys will check it out.
I was holding the trunk release down and the alarm went off. I thought that's how it worked as for my other car I need to hold the button to pop the trunk.

Doors were closed, maybe trunk wasn't shut properly.
While on the matter, the trunk takes quite a bit of a "slam" to shut. Is this adjustable somehow?

Well that makes a whole lot of sense. Im assuming our boots lock isnt fully engaging every time which is making the car think the boot is still open. I know Ive seen the strikes loosened and knocked for adjustment on other cars, but cant say for certain whether our are adjustable (sure someone could assist here or we could just try). I wonder if maybe the locks casing is slightly bent up...
I didnt know holding the boot set off the alarm. I knew holding the red sets off the alarm and only just found out holding the boot button will do the same. Though its double click to open the boot for me.
On the topic of boots and remote opening... Do any Magnas boots spring open? I know mine doesnt, but having a spoiler would weaken a springs attempt to open my boot on its own. I love boots that pop themselves open! Great for when you have your hands full of shopping and are over relying on your karate kicking skills to open it :)

Mine springs open about halfway but not enough to actually put anything in through the opening.
No spoiler on it though

That is definitely better than almost nothing! Though a worthy price as I do like my spoiler. Just want the best of both worlds naturally :)

I think you might be able to adjust how much tension there is for it to spring open?
Though I doubt it'd be worth the hassle

Whether the effort is worthwhile or not is relative to how much a person wants their boot to spring open. I really want it! Though even if they are adjustable, I doubt it would ever fully lift the weight of the boot. I will took a look anyway...

Could be the actuator on the driver side door. Search it up common problem

No it turns out it was the trunk lid. If I open it and close it again it then locks without beeping