Thanks for reporting this, it actually worked when you followed the right process it was just that the messages weren't in the right order so nobody knew how to use it. I've fixed this so they appear in the right order and now it makes sense and works.
The way you rob Energ's ammu-nation is actually as follows:
1. Go to the black market & purchase a keypad unlocker.
2. Make sure there are two of you spawned in the same group.
3. Use /partner [ID] to partner up with someone in the same group.
4. Make sure your partner is sat in a vehicle outside the ammu-nation front door.
5. Go up the stairs and press [Y] to start the keypad hack, memorise the code and re-enter it.
6. Once you are in the room you'll see "Press [F] to pick up weapons" - press F.
7. You will now have completed the robbery, head back outside to the car and get back to the group base.
8. Go to the weapon rack and refill it - it will be the only option when you use it if you have stolen weapons.
Update will be on the server midnight BST tonight