Can you double check if you have inserted your SD card properly.
If you have inserted the SD card properly and if the Green LED remain solid and don't flash, then the SD card might be corrupted.
Can you tell us if you are using the SD card bought from us or your own SD card. If you are using your own SD card, then you might have to re-burn the image onto your SD card and try again.
If you have bought the SD card from Dexter Industries, we will have it replaced, please send us a request here. However it will take some time for the SD card to arrive, if you don't wish to wait, you can follow the guide here to burn the SD card and try it out.
Please let us know if this helps,