PO approval does not disregard the charge account on the cancelled line

We are on 12.1.3 and use supervisor based approval process.(not position based).

We have this issue in production where a PO intially had one line with a charge  a/c# 521400 which was incorrect so the approver rejected the PO and sent it back to the buyer to correct the line.(No one as approval authority for this a/c #)

The buyer cancelled the line and added a new line with the correct charge a/c# 521300.The total $ amount on the PO = the $ amount for line2(line 1 is cancelled)

The PO was again sent for approval but we noticed that the PO is not getting approved by the approver who has enough approval limits to approve a/c#