During the last conversion cycle, we encountered an issue where 2 AP invoice records failed in the TEST instance without displaying any error message. In the interface table, their status was marked as REJECTED; however, when we checked the AP_INTERFACE_REJECTIONS table for the rejection reason, we could not find any corresponding record

Ex - Upon running the below query in Fusion Test instance 
SELECT * from AP_INVOICES_INTERFACE where LOAD_REQUEST_ID = '3152041',
We were getting 2 records with Status as 'REJECTED'
However, the below query  
SELECT * from AP_INTERFACE_REJECTIONS where LOAD_REQUEST_ID = '3152041'
not returning any records

We raised an SR for this issue (4-0000634507), and were advised to submit an enhancement request by logging an idea.