me: ...Without knowing I can only speculate the Altkey field in your ‘shape file’ is numeric while the Altkey in your table is text. Emphasis on speculate...
you: All fields in the imported table are Text except for currency values which are Double.
Push yourself away from the desk, and take a breath. This is learning experience. I've said this a thousand times before and @DanPatterson knows where I stand when it comes to excel; it's great to do taxes with, but as a data management tool, it's not so great.
All that said, take a few moments to examine your data in both the shape file and table/excel worksheet. As Dan mentions, empty fields are often the the wrench that gets tossed into the cog.
That should just about do it....