I get the same response for an App that is _definitely_ not a Ringtone..
"
Ringtones detected
Your APK includes a manifest declaration and/or an API invocation that indicates your app is a Ringtone.
Note: Ringtones are supported by the Amazon Appstore on non-Amazon devices. You can submit your APK without fixing this issue, but your app will not be displayed in the Amazon Appstore as being compatible with Amazon devices.
"
I've submitted it for an actual test... Will see what they say. My Apps work on all current Amazon devices apart from the TV.