Whenever Order Entry does day end processing, it either creates a new invoice batch in AR, or it writes to a retrieval invoice batch for AR, depending on which option was selected in the OE company profile when day end was done. This AR invoice batch has to be posted in order to update AR current transactions, and it has to be paid (or credited or adjusted) for a current balance of 0.00 before it can be moved to AR history.

If you are in AR and go to the Maintenance function and Retrieve invoice batches, is there anything to retrieve from OE?

Are there any matching transactions (payments, credits, etc) for this customer that could have been applied to this invoice (to verify it ever made it to AR)?

Are you aware if the GL transactions include this invoice? It would involve searching the posted GL transactions for the document number - should you choose to send the OE or AR document numbers to GL reference/description fields.

Is the GL clearing account between OE and AR equal to zero? This account is defined in the OE company profile - 'AR clearing account'?

It could be that Day End was interrupted - though this would result in GL, IC and tax reports also missing remnants of this invoice. Or that the invoice was never posted in AR and rather the batch was not retrieved or deleted. Or the invoice was purged out of AR history. Or other possibilities that other readers may come up with.

Does your data AR and OE) pass an integrity check?