What can make the gear show its in drive but when you look at the dash its in neutral?

When you try and park my Rodeo it wont go up to park it stops in neutral, and when you move the gear to reverse and look at the dash it says its in drive. I don't understand. It seems as if the Park and Reverse are not able to be used anymore and that Neutral is as low as I can go. I am having to use my parking brake so I don't roll away.... Any suggestions ???