I'm encountering the same problem (billing document posted but no accounting document generated), but the SO has an amount greater than 0.00.
I've done the ff settings already:
1) Billing Type's Account Determination to the standard KOFI00.
2) The Doc Pricing Procedure is same as the SO Doc Pricing Procedure.
3) The AccountAssignmentGroup of both Material and Customer are defined at the master data.
4) Corresponding Account Keys (ERL for Revenue, MWS for Output Tax) were assigned to pricing procedure used
5) Revenue GL is already assigned to combination: Application (V)-Condition type for account determination (KOFI)-COA-SalesOrg-Account assignment group for Customer-Account assignment group for Material.
Did I miss out something?