Thanks for that Shear Tip and Stribo.
I have established the problem based on your information. I was not pushing the memory card far enough in, so it was being pushed in by the lid when closing. However this has pushed the rubber coating. So now the rubber coating will not push the memory card far enough in.
However I pushed the card in further and it clipped into place, solving the problem. Thanks again!

Pointman, I found that if the card is read only, it will be recognised by the GT-11 when it starts up but then there is no further action. Thanks for the info too.