OK so when I try to save my game on my playstation 2 memory card it says memory card not inserted but there is one in the slot... what should I do?

Have you tried pushing it in harder so it's all the way in, or removing it, then pushing it in hard again? Is there enough memory on it?

Has it worked before this?

There is enogh memory on it cause I just deleted most of the things on it yesterday and I haven't played my playstation 2 in forever so I don't know how long its been like that and I will go try to push it in harder right now.thanks for your suggestion(:

Try with any other slot if you have one.