Below are guideline(s) to settle issue when Item Menu / Button is Blocked on Invoice

Step 1: Go to System >> Administrator Menu >> General Setup

Step 2: Go to System Setting >> untick “Compulsory Delivery Order” >> click “Save”

If u Tick the Compulsory Delivery Order on General Setup System Settings, it will make Item Menu On Invoicing Blocked so it will be compulsory to issue Delivery Order first then only can issue Invoice