- Make sure Spark has enough power to work properly. Try plugging it into USB, and uploading the RGB example if you're unsure.
- Make sure that the code you're using uses the LCD. If in doubt, use one of the LCD examples.
- If its still not working, make sure the connector isn't loose.
If you're still having issues after these steps, try contacting support, and be sure to mention what you've tried so far, and if it was ever working before.