Komputerbay card works OK on PC/Mac but the 5d cant read it.

[premini]

Hi, a year ago i bought a Komputerbay 64gb CF card. it didnt work and it was not accesble from my win 7 PC. Amazon returned the cash and they didnt even mind of asking me to return the card.
Now i bought a macbook and surprisingly it could format it and the card now can be used in both pc and mac.
the problem is that my 5d3 still shows a message asking me to format the card and when i try it it says "Cannont format , change card1".
Question: is there any low level editor or trick i can do for getting the 5d to read the card?
Thank you very much in advance.

[jimmyD30]

Which format did you use on the Mac? Try FAT32 or exFAT.

[premini]

I tried ExFAT.

[jimmyD30]

Try reformatting to FAT32 with the PC, maybe some luck.

[premini]

No luck with FAT32 unfortunately.

[Frank7D]

You could test it with this:
http://www.heise.de/download/h2testw.html