I have a Canon Camera that when I open the place to put the Compact Flash (memory card in, that camera does not work anymore and after says error, that's all and without the card it works.
If it's an older camera it may not accept a card of a size above certain limits -- see camera spec or manual and see if it mentions a size of card -- that may have been the largest made at the time the camera was released..
Problem can also occur if a card of any size has previously been used in another camera or device. In that case you need to reformat the card in the Canon.