EOS 5D Mark III does not access card 1 or 2 - formatted on Mac - Help?

[nounasworld]

Hi , i  just started using this camera Canon 5d mark iii, its used . 

I finally used it for a full day creating photos and videos , it was working perfectly ,and after that ,when we removed the card to copy the files on the computer ,my Canon would not ready neither the compact flesh card that I previously used neither a new one that I tried to insert. I thought I lost everything , it was saying to format the card , once I connected the card reader to my mac I first saved everything and then formatted everything , and thought I solved the problem.

Still after formatting, my canon does not read any cards. It says " CARD 1 CANNOT BE ACCESSED - REINSERT / CHANGE THE CARD OR FORMAT CARD WITH CAMERA .

but it doesn't show any card, and even when I press FORMAT CARD 1 says CANNOT FORMAT - CHANGE CARD1

Obviously I did format it on my mac . so it makes sense. but why then does it not wanna read it and tells me to format it again ? 

What shall I do ? 

[johnrmoyer]

I suggest only formatting the memory cards in the camera and not in a computer.

There is some variety in how file systems are implemented https://en.wikipedia.org/wiki/Design_of_the_FAT_file_system and the camera will use the version that the camera understands.

If after formatting the memory card in the mac, the camera refuses to format it, then I suggest that the memory card might be recovered by formatting to MSDOS (FAT) in the mac and then formatting it again in the camera.

https://support-en.sandisk.com/app/answers/detailweb/a_id/35101/~/steps-to-format-a-memory-card-on-m...

[TomRamsey]

Always format it in the camera, I have that there is a format that you can use on a computer, but it is not the normal formatting the computer does.  Anyway, cards should be formatted in the camera you are using to avoid problems.  I format after every time I upload files.  I also prefer to upload via cable ot WiFi because I think it's less wear on the card, and sometimes computers want to format cards