Received Not Invoiced report not matching the Balance Sheet account
The Received Not Invoiced GL account on the Balance Sheet should match the (Purch > Reports > Received Not Invoiced) report as long as:
1) Everything is currently Batch Posted under (GL > Batch Posting).
2) Nobody mistakenly set up or changed something with Account Assignments in the past.
3) Nobody made Journal Entries to that account (or made a mistaken entry during implementation of DBA).
If you've posted all GL transactions, and there is still a discrepancy between the Balance Sheet value and the Received Not Invoiced report, then you'll need to make a Journal Entry to the Received Not Invoiced account so that it matches the Received Not Invoiced report. It should be the final Journal Entry you ever make to this account. As with all Journal Entries, our recommendation is to have your company accountant review the entry prior to posting it.
Also, just as a side note, prior to doing all of this (and on an on-going basis), make sure you close all PO's that are to have no further action upon them. No PO's should be sitting around open if they're no longer to be actioned upon. Closing PO's helps clean up old data sitting on the Received Not Invoiced report.