I am trying to do the first backpack. I'm near the end but when I add new allocations the total cost is $0, as you can see below with Vendors. I keep trying to mess with the distributing but everything I do still keeps the allocation at $0. If someone can give me some insight on what is supposed to happen here I would really appreciate it.  

Did you check the Vendor Master Data.Count field?  The allocation is weighted by that field, but if all the records are zero or blank, then it won't allocate anything.

Thanks for the reply! I'm still pretty new at this so I'm not sure I totally understand. I have the Vendor Master Data.Count box checked (in the second picture) but everything is still allocating to $0. And when I uncheck it, the same thing happens. 

What I was referring to was actually going into the Vendor Master table, and looking at the values in the Count field.  I'd still look into that, but if it doesn't allocate even if you have the Weighted By box unchecked, then that may not be the issue.  I'd probably start looking at my unique identifiers next.  Find one in Cost Source that you know should be in Vendors, and then go look for it in Vendors.

One thing that I always look out for in unique identifiers is leading and trailing spaces.  If one of them has a trailing space and the other doesn't, then they won't match.  I always like to use the Trim() function in my identifiers just to be sure that doesn't happen.

It is also helpful to make sure you have matching keys in both data sets.  This is what the spend will match on and flow up through the model with.  Have you confirmed this?

I was able to figure it out, it was a dumb mistake. I meant to have my data filtering from the Cost Source where Vendor equals Yes and Labor equals No, but I had Vendor equals Yes and Vendor equals No. 

Thanks for all the replies though. I definitely feel like I have a better understanding on how this works because of them. 

Glad you figured it out!  It's always satisfying to fix something that's broken... even if it was broken because of a "dumb mistake"!