Whenever I try to engage the altitude hold in my IADG A320, the plane just nosedives into the earth. There is probably some easy fix for this, but I don't kow it. Can anyone help? Thanks!

Hopefully you have set the altitude you desired above the altitude you are presently flying. If not, set you desired altitude prior to leaving the gate. That way, when you select altitude hold, your aircraft should go up and not try to zoom to "0" altitude.

I set the altitude before I takeoff. This one plane just causes problems.