PO acknowledgement required emails sent to most recent contact on iSupplier portal

Hi,

We are on R12.2

1)Created 5 supplier contacts for the same supplier with iSupplier portal access .

2)Created a PO with acceptance required for the same supplier

3) I expected all the suppliers will receive 'PO Acceptance required' notifications.

4) However only the most recently onboarded supplier contact received the email notification, even though all other iSupplier contacts are active and have same access.

How can fix this ?

thank you,

Daniela