Camera cannot read or format specific card

I've had a Canon T2i for three years now, and have been using the same two cards: Transcend 16 GB class 10.
All of a sudden one of them stopped working on the camera. The message "Card cannot be accessed. Reinsert/change the card or format card with camera" appears. When I try to format it with the camera, it says "Cannot format. Change card".

When I insert the card directly in my Macbook, it works just fine, I saved the photos that were in the card. I formatted it on the Macbook and the camera still won't recognize it.

The other memory card, the same brand and size, works just fine on the camera and macbook.

I can't seem to find the solution on Google. Please don't tell me to buy a new one, I know I have to, but I can't right now. I just need this one to work.

anaz wrote in post #16272028
...Please don't tell me to buy a new one, ...

OK, I won't.... but that is probably the only solution.

Examine the card carefully for physical damage or anything else that would affect the connections between the card and your camera. You might try cleaning the contacts. Other than that, ... well, you know...

One other thought... make sure the little slide "lock" switch is unlocked. This does nothing to the card itself... it is like the punch-out tabs on old VHS tapes in that it depends on the "host" device to pay attention to it. I don't know if Canon cameras read the position of that slide or not, but the chances are pretty good your mac ignores it.

Many, many years ago, for my Canon G2 I had a CF card fail to where the Canon camera could not write new pictures to the CF and in-camera Format would not get that CF to be acceptable by a Canon camera. But the CF could be fully read by a PC and even could be written on by a PC! Formatting in PC would not make it writable in the camera either. I gave up using it in my camera and put it into a digital picture frame.

anaz wrote in post #16272028
Please don't tell me to buy a new one, I know I have to, but I can't right now. I just need this one to work.

Do you =REALLY= want to trust your pictures on a card you can no longer depend on??? After 46 years in computers, from punch cards till now, I've learned one lesson the hard way too many times...If it's not 100% reliable, fix it or replace it...but NEVER use it until it works reliably!

bratkinson wrote in post #16275317
After 46 years in computers

...they let you out finally, on parole for good behavior?!