In order to upload an Android app which uses the Google APIs (maps) Amazon requires that you upload an unsigned binary.
From the Amazon App Management portal:
7. Upload your unsigned binary (shown as Step 1. Upload unsigned binary)
Using MonoDevelop and Mono for Android, how do I create an unsigned binary for Amazon?
Every time you deploy to an emulator or device, both a signed and unsigned package is created. Check in bin\Release to find a pair of files like:
The one without "Signed" is the unsigned package.