Invoice Approval problem

Hi All

I am attempting to set up Invoice approval - requirements are to initiate approval for all invoices not matched to a PO.  PO matched invoices do not require approval.

I have a rule set on Condition - Supplier_invoice_matched in (N) require one level of supervisor approval.  When I include the seeded rules Invoice Header Match Check and/or Invoice Line Match Check (conditions Approved Matched Invoices/Approve matched Invoice lines = True), all invoices are then set to Approval not required.  If i do not include the Invoices Header match check the workflow fails with AT_LEAST_ONE_RULE_MUST_APPLY