I finally figured out why my MARTA card kept failing at the gate
For 5 weeks I kept tapping my card at the Lindbergh Center station and getting the red light, and I blamed the card reader. A station agent named Marcus took one look and told me the plastic sleeve I keep it in blocks the chip, and that's why it worked fine at Kroger but not on MARTA. Took it out of the sleeve and it's worked every time since, so check yours before you waste a trip to the service window. Has anyone else had a card sleeve mess with the readers at other stations?