This happens when there is an invalid ACH item that can't be posted at all (bad account number, for example).  Even if you subsequently update it, when reposting if the item can't pay due to non-sufficient funds, the NSF fee will not automatically be charged.  The ACH item will also not show in the member's transaction history.  That's because NSF fees are only charged when the item originally comes in, not via the ACH Exceptions re-post feature, to prevent these fees from being double-posted.

On an invalid item like this, the NSF fee has to be manually charged. We recommend posting a debit and credit to the account to show the ACH item trying to post, then reversed as NSF.  The account adjustment can also include the NSF fee.  Here is an example: