Box 20 is blank on my w-2, but it will not let me submit my taxes with that box empty. I even tried manually and uploading a pic. Any suggestions??

Make box 18 blank too, not even a space.  Do you have anything in 19?  Then you need something in 20.  Ask your employer.  

If there is an amount in box 19 (local income tax withheld), then you must identify the local taxing jurisdiction (city, county, school district) in box 20. You can type something in yourself, even if your actual W-2 is blank. 

If box 19 is blank or has a zero in it, then all three boxes (18, 19, and 20) must be blank. Not even a space. If box 19 has an amount greater than zero in it, then boxes 18 and 20 "must" have something in them also.