Is the shifter not going into drive? may have a problem with the shifter itself. Does it move in reverse but not drive then your transmission may be low on fluid. Check the level with the engine running. If the fluid level is full and it still won't move in drive. Look at the color of the transmission fluid( wipe the dipstick with a white cloth or paper towel ) . If the color is dark brown or black then you are looking at needing a rebuild or replacement. If the color is pretty pink then you may need the valve body replaced/repaired.( located inside the transmission.) but not a complete rebuild.