If you created vendor bills in CORE for the work your vendors did, but instead of paying them using the Bill Payments screen, you cut a check directly to your vendor. This can lead to problems with your accounting, which is often realized when reconciling your accounts. Because the vendor bills remain unpaid, your accounts payable (A/P) shows aging when that is not the case.
To fix this, you can start by paying your vendor bills first (via check). After that, you can make a journal entry to clear the payment made to the vendor and increase your A/P amount.