If you really want to troubleshoot the problem you are going to have to isolate the problem. Meaning, is it the device or is it the card? Once you've isolated the problem, then you can take the appropriate measures (you will know either the tablet port is funky or you need a new card).
So, you'll have to either put a different card in your tablet, or you put the card in a different device (laptop, phone, another tablet).