I did a couple of things to troubleshoot and here's what I got.
First, I added the DFP upload behavior. It didn't work either.
So I added-
It gave me an error about moving the temp file and me not having permission. I double checked all my paths and testing server as you recommended. Then I went through my MAMP Pro step by step again and realized I had made a change under "General".
The part where it says "Run Apache/MySQL server as user". I had change it way back when I installed MAMP Pro and forgot about it. The reason I changed it was because it recommended that I do. With username/username selected a red warning comes up that says [color=red]"For security reasons, it's recommended to run the servers as 'www/mysql' when your Mac is connected to the Internet."[/color]
So I changed it to www/mysql and the warning went away. Turns out I was causing the problem the whole time. I hate when I do that.
Everything is working now.
On the subject, are there any security issues keeping it on username/username? I'm always connected to the internet.