Problems W/Hyundai Elantra

Just wondering if anyone could help me with other car problems... My 2010 Hyundai elantra will currently not shift out of park. you have to hold the release button for you to move the shifter to drive or reverse. Once in drive, you can move it to neutral, 1 and 2 but not reverse or park. it locks you out of those and i do not want to force the shifter up and break things further... You can go to any gear while holding release button. if you are in reverse or park you are stock in those gears until you hold the button again. Wondering if a cable is lose or sensor is bad?? Car is a automatic.