SUMIF Function With Dates Not Working?

Hello Excel Maestro's,

I have a really simple question and I'm completely frustrated because I've tried working the SUMIF formula a couple different ways. I've attached sample with only the relevant info I'm trying to query. sample.xlsx

Essentially I'm trying to sum units for a particular day in range AD4:AD11 and the corresponding days are in AA4:AA11. My Units are in range H6:H6406 and the list of dates for the Units are in range B6:B6406.

Current formula I'm trying is:

=SUMIF($B$6:$B$6406,B6=AA4,$H$6:$H$6406)

What am I doing wrong?