Nikon d3100 won't read SD card how can I fix it?

When I plug it into the camera it reads as -E-
it is a SDHC
it has worked on the camera before
I had used it for ready boost on my laptop now it dosent seem to work
I have tried reformatting it.
it is no longer configured for ready boost.
help?

Added (1). It's not locked either

Added (2). The computer reads the card fine. The camera also reads other cards normally

Yeass

Buy a new card.