There was a bug introduced last minute when we updated to the newer Esp32 file manager that caused the audio mappings file to not be generated at startup. There was also a minor issue where if you reloaded the uid control page it was possible that the websocket was not ready yet. In this state, the reader would not be put into scanning mode and the field would not populate.
No breaking changes or configuration updates required. Just flash this new version to get the bug fixes.