My digital camera is not reading any memory cards,?

...it used to, it's not old, sup with that?

Try to format you card on your computer through a card reader.
if the problem is still there
try another memory stick which is the same type with your current memory stick at some shop (no need to buy b4 test :D) to test if your memory card stop working or your camera card reader.
Good luck!

Memory card could be dirty or scratched or something?