If speech to text is working but STT_MicrophoneBuffer is never called, it sounds like the recording callback is not being triggered. First check that you are using SpeechToTextRec correctly and that the buffer event is enabled in the library settings. Also make sure you have record audio permission granted at runtime, not just in the manifest. You can try adding a log line inside STT_MicrophoneBuffer to confirm it never fires, and test on another device to rule out a device issue.