EOS

[Copperhen]

Just want to say thanks to JoeN. My sd slot was not reading at all, said there was no card in the camera. After trying several different cards with the same result, I found your suggestion. I removed the CF card, turned on the camera with only the sd and HOORAY. Many thanks.

[barrisster]

The only thing I can suggest is that you either have a bad CF card or one of the pins is bent.  Change cards.  if that does not work look to see if all of the pins are straight.

[dalegriner]

I just bought the Mark IV and I am having the exact same problem.

[Philushka]

Tried several cards.  Pins not bent.  It turned out to be a problem inside the camera.  

Thanks for your response though, Barrisster.  Much appreciated.

[santrupt1]

I just purchased Mark IV and barely used it for one trip; took out Lexar CF card to transfer pictures to my computer. Now I am getting same problem, the CF card is not accessible. Camera doesn't even format the CF card. Any suggesstion where to seek help? Thanks.

[Towfiq5472]

Same problem with my Mark III. I use Sandisk class 10 card. When this problem first appeared I reset all the camera settings and then it was solved but now it’s stuck. I don’t know how to solve this

[sin41]

should be the bend pin in your camera. I had the same problem and fix it with a tiny crew driver.