Why is Person Responsible the same in P43070 after Delegation to a new approver was already done?

9.2.7.2

We made a change in PO approval routes. We delegated all POs under a user to the new user who would take over PO approvals. Now, we are running into the issue of Purchase Orders still being under the responsibility of the old PO approver. So, now when users want to receive those Purchase Orders they are unable to and we have to release them thru P43070.