Hello Sanket
Greetings for the day!
I would like to tell you some basic things still if your issue has not resolved after the above help given by our SAP guru's.
1. In SPRO, under AR&AP, Customer Accounts, Line Items, Display Line Items, Display Line Items without ALV. Check the basic setting there
2. Please check the Field Status Group, whether that field is in supress or display mode instead of Optional for that GL Account or for that Document Type/Posting Key also. Thanks
Best Regards
Venkat