G/L account not taking in A/R Invoice

Hi Experts,

I have an issue that G/L account not taking in A/R Invoice ( Revenue Account ). Inventory method by Item group. It's not happening for particular items or particular item group. for the same item, taking correctly in some invoice and not taking in some invoice. In Item Group, all accounts are mapped correctly but not taking automatically in invoice. I need to make visible G/L Account from form settings and need to select manually in this kind of situations. am using 9.1 PL:01

please give me your valuable suggestions on what will be the reason for this.

Thanks

Fahis T