In order to successfully capture the sound in your video using the T Uploader app, you must first make sure that the app has access to your iPhone or Android microphone.
Recording with iPhone:
Navigate to your phone's Settings → Privacy → Microphone. In your Microphone settings, make sure that the application "T Uploader" is set to ON by tapping on the button so it turns green.
Recording with Android:
Open your T Uploader app and click the gear icon to go the app Settings. Tap Choose audio input" and select the built-in microphone.