Vintage Sony M-19V Voice Operated Recording Plug In Recorder (READ DESCRIPTION)

Vintage Sony M-19V Voice Operated Recording Plug In Recorder. I have tested the recorder. It does work using batteries but the internal rechargeable battery does not seem to hold a charge. It will play, fast forward, and rewind the micro cassettes. When trying to replay a test recording I did not hear anything. Unsure if it didnt record or didnt play properly.