I've put all the add-ons from the zip file into my add-on's folder and I'm still missing bricks. Here is all the bricks it's saying that are missing:
All of the bricks listed there are in Brick_DemiansBB3.
First, confirm that you have that add on enabled.
Then, make sure that the only brickpacks enabled are the ones that I have in the download. I say this because some other brickpacks (Chao's Essentials, for example) conflict with Demian's when both of those packs are enabled.