There tends to be a few things to check when this happens repeatedly:
1) Are the rules in your smart campaign allowing you to "run through the flow every time". If it's "just once" you won't recieve any emails, if you're doing QA and not using the test email feature.
2) If you are using the "test send" feature, sometimes there can be a delay on the servers OR it ends up in your SPAM folder because it contains the "test" feature. The easiest way to remedy this is to add the test emails as "appoved" in your SPAM program (which obviously differs depending on the program you use). We use postini and it took a few rounds of telling postini that our tests were not spam for them to work.
I would recommend sending yourself the email for testing through a smart campaign used only for testing. This ensures you see the email the way all your recipients will.
Hope that helps!