SD Billing Block will not worked if you did not assign it

Define the possible block indicators in SM30 - V_TVFS

and

allocate them to the billing types concerned in SM30 - V_TVFSP.

Your Billing Block will not worked if you did not assigned it to the desired billing types.

You can auto block by :-

1. sales document type in transaction VOV8, fields Billing Block,

or

2. item categories in SM30 - V_TVAP, by filling the fields Billing Block.