VLOOKUP returning an #N/A when it should return a value

Hello,

I have attached a workbook to this post that uses this formula:

=VLOOKUP(C5,Sheet2!$B$1:$C$99,2,0)

in Sheet1. The value in C5 is a value produced from another formula. I've carefully checked my work, but I am still getting an error. Can anyone tell me what I am doing wrong? I encounter a similar problem from time to time, and I'm hoping this will help me understand how this formula works a little better. I have a feeling that this has to do either with cell format, or placement of the cell with the formula in relation to the data it is reading.

Big thanks to anyone who can help at all with this!