From what I've read it's normal. There may be some microscopic food in there for them that they're finishing up. I think it may take up to a month or so before the majority of them move up but I'm sure some will remain in the bottom bin and you'll have to separate them out of your finished vc.

I'm sure someone with more knowledge on the subject will chime in because I'm still new to vermicomposting.

Understand that what we call food and what the worms consider food are two different things. The worms eat the microbes that decompose the organic matter we place in the bins. As long as there are microbes in the lower bin, some of the worms will prefer to stay there. In two weeks I would expect more than a couple hundred worms to move up, but not all of them will, no matter how long you give them. When I still had my worms, I allowed 3 months for the worms to move up, and I still had a few stragglers in the lower bin.

Sbryce if there was a point system I'd be giving u +1 but since I can't please pat yourself on the back for me.

When I said microscopic food I meant the microbes they survive off of but didn't know how to go into detail about it.
I wonder how many worms OP started with and how long has the system been running?

If you scroll to the bottom of the link I'm about to post someone suggests their way of getting stragglers that didn't want to move up.
http://vermicomposters.ning.com/forum/topics/worms-not-moving-up?commentId=2094123%3AComment%3A64568

Thanks for the +1, but I get a lot of practice. This is the second time this week I have answered the same question.

Sbryce - I put my question in then saw the same ? from Saturday. appreciate your answer. I am going to try a 3rd tier with food to try to pull the worms up. Your thoughts>

Mike

If a second tier isn't drawing worms up, a third tier won't either. Save the third tier for when the second tier is mostly full of castings.

You might try what I do with single bins when time is nearing to hearvest castings. I use the piles in bright light method to drive worms to bottom of pile then remove top castings. Put remaining castings along with worms back into bin,add new bedding and start feeding again. Kinda fast and dirty but suits my lazy style of gardening.