I have two white elevators 15 blocks apart, I can go up but not down.

In recent version elevators consume XP. This can be disabled with config options. Please check, if it works when you have some levels.

Oh, wait, sorry, read that wrong. Are you using modpack? Version is there is quite old, and bug may be already fixed right now.

I had a similar problem, mine was I could go down but not up. I actually placed a torch one block above the top elevator which would throw an error and not let me go up, could that be your problem?

Make sure you're using the latest OpenBlocks and yes you need two air blocks above each elevator block