I'm sorry you're having audio issues with Skype on your Fire tablet. You've done a great job troubleshooting so far. You may have tried these steps already, but just to be sure we're covering the basics I have a few questions. While on a Skype call, are you turning up the volume on the tablet's volume buttons, and if so can you hear it increasing? Are you turning on the speaker while in call or using an earpiece? Is this happening with multiple contacts or just a specific person? Have you tried a test call, and if so, how did that go?