Sega Master System Sega Card trouble!!

[Shrooin]

I recently acquired a couple Sega Card games but both don't work on my SMS 1. It plays cartridges fine but whenever I try to load up my sega cards I just get the built in games screen. I bought the Sega Cards from an ebay dealer, other people left him positive feedback who bought cards. So is it possible the card reader in my SMS is broken or is it the Sega Cards that are faulty? Is there anyway I can find out without buying another SMS? And I don't know anyone that has one to test it out on

[OdSquad64]

try cleaning the contacts on the card with alcohol and q-tips or if that doesn't work try rubbing them clean with a eraser. if those don't work, i think there's a way to clean the card slot with a credit card, but I'm not familiar with that method.
and remember, just because the contacts look clean doesn't mean they are