can't type input into CA Form 568 worksheet line J business code box

[hooha]

In California Form 568 the program won't let me type anything in the box on line J where you're supposed to enter the business code.  I know the code, and never had a problem with this in past years.  I tried to figure out which supporting document might need to be filled out to populate that business code box automatically, but can't find one.    (This form  has to be printed out and mailed in California, so I guess I can fill in the code by hand, but I'm worried that could screw up the processing of the return.)  Help will be much appreciated.  Thanks!  (TurboTax Home and Business 2019, Windows)