Getting a 403 Forbidden error when I try to log in on the Wordpress iOS app

I'm using Automattic's iOS app for Wordpress and I'm trying to log-in for the first time to my site. I clicked the "add self-hosted site" option and put in the username, password and my self-hosted wordpress blog, and when I try to sign in I get a 403 error spit back at me.

Any ideas?