OK let's recap. Waddizzle and I have been doing this for a very long time. Decades in fact. We are only offering what we have seen over those years of experience. Is it possible to get a good SD card from Amazon? Yes it is but that's the issue. You don't know because you don't know which supplier you are getting it from because you most likely chose the lowest price supplier..
Can you get a bad card form a source lie B&H Photo? I imagine it is possible but so unlikely that it is nearly impossible, to impossible. B&H Photo, Adorama, Best Buy, etc., and other top retailers buy directly from Sandisk. When buying from Amazon and the lowest cost provider you never know where they get the SD card from. Chances of a bad or counterfeit product is high, very high. This is also true with batteries another highly counterfeited product. Sometimes these counterfeit products work. However, you can never trust them and some can be dangerous especially counterfeit batteries.
Now back to why your camera can't read the SD card. First we do need to prove you do have a good SD card. Does your Windows computer read it? Can you format it on your Windows, not a Mac, computer? If these questions are yes, the SD card is probably OK. If not buy the exact SD card recommended in your manual from B&H Photo. Do not as recommended above buy or use a micro SD card and adapter. Buy a full size SD card. Format the SD card. Reset your camera to default condition. Take some shots and see if you can read the SD card. If you still can not call Canon to set up a service order. 1 (800) 652-2666
EB
EOS 1DX and 1D Mk IV and less lenses then before!
