Each peice of seige equipment costs build points, and at least one turn to build. I think you qued up the ladders, but then immediatly hit the play battle button. Sicne the ladders hadn't been built yet, you didn't have them.

If you're sieging a town with a large stone wall or epic stone wall, the ladders won't show up. You can only use ladders on regular stone walls. Use siege towers instead.

It's a bug.

I dont think the ladders would reach an EPIC stone wall.

That depends completely on how log you make them.

I can only assume steace is talking about in real life and not game mechanics, but even then, making a huge ladder isn't going to solve all your problems. For the same reason that you can lay a 2x4 over a small gap and use it as a bridge, but the larger the gap, the more the board is going to bend in the middle.

Trying to make a sixty-foot ladder is going to test the tensile strength of the wood much much more than a thirty foot one. Requiring a siege tower seems fair to me.

But a ladder is placed almost vertical, and you just have to make the ladder thicker and longer. It will take you more time, and it will be harder to get them to the walls quickly, but it IS possible.

ladders for an epic wall would be just too heavy not to break, you would need some kind of ballista equipment like you see in the two towers to hoist them up.
And pretty suicidal men to climb up.