Keywords: SP850, micro SD card, no sound, TF card
If insert your micro SD card, but LCD screen shows "no SD card installed," or words to that effect, this is most likely because:
1. Micro SD card isn't working correctly (can't be read), you can test it using your phone or other device.
2. It cannot read micro SD cards larger than 32GB, check your micro SD card capacity.
3. The speaker supports music with MP3/WMA/WAV format, check the format of music.
If you tested above solution and no fix, there is a possibility of an unfortunately non-working unit, then we can arrange Amazon return & replacement for you to check.