Witholding tax not calculated for interfaced invoices

All, Witholding tax setups done until now. 1) Created a Tax code with create withholding tax group enabled. 2) Tax group automatically created 3) Supplier - Tax Details - Header level - Allow Tax Witholding checkbox is enabled 4) Supplier site level - Tax Details -  Allow Tax Witholding tax checkbox is enabled and tax group is associated Invoice is brought in thru interface and the Invoice Witholding Tax Group is defaulted at the invoice line level. However, when validation of invoice, the tax line is not calculated. Alternatively, when I  manually query the invoice, re-attach the Invoice Witholding Tax