You do not have the right to modify this record, because this record printed 1 times before, do you want to ask your supervisor to pass this permission? 


GOTO General Maintenance > User Maintenance

1. Select User Code

2. Select Control tab

3. Search for ‘Modify after Print Out’ there are two option purchase and sales module.

4. Option table to ‘Allow’

5. Save

Done. Thanks

Download Full Document here