So I put my car in reverse and it wount move whats going on! on 1997 Plymouth Grand Voyager

So I put my car in reverse and it wount move then I put the car in neutral and it moves forward I added transmission fluid but nothing has changed please help me don't know what else it may be

2 answers
Most likely, is that your transmission range sensor has gone bad. It is reading a gear other than what you are in and thus, the two are no longer in sync. Need to put a new transmission range sensor in.
http://www.2carpros.com/forum/automotive_pictures/99387_Graphic9_30.jpg
HOW LOW WAS YOUR TRANS FLUID