This is the top of the drive, with the front of the unit facing the left side of the picture. On the very bottom of this picture you can see the disk ejection switch. The plastic housing itself has that L-shaped arm that throws a thin long black plastic lever down, which in turn closes the circuit of the brass plates to signal to the system that a disk card is inserted. You want to check what is going on here first. When there is no disk and the assembly is in empty/ejected position, that lever should be raised by itself under spring tension.