Sum of Drop down Lists

I have created a list of categories for a budget.  Then on another worksheet I have all my checking account transactions.  I already created the drop down list to categorize the expense.  Now I want excel to sum all the expenses based on their category.  I keep trying to use the SUMIF function, but for sum reason it is not working for categories that I have multiple expenses under.  Please see my attached file.

I want the totals from the monthly transactions to go into the corresponding month on the first worksheet.