OK, I can’t explain why you are getting an AP to connect, but the LED is reporting a problem with the SD card. If you are comfortable with opening the it up, there are four screws under the rubber pads which just pull out. Remove the screws and open it up. The SDcard is in the back of the board. You can try removing it and reinserting. Then try to start it again. Careful to never remove or insert the SD while the device is powered up.
If the problem persists and you have a computer with a miscrSD card reader or an adapter, try mounting the card and see if you can read the directory.
If you are not comfortable with any of this, you can contact OEM and return it for them to sort it out.