Buyer not receiving Notification

Hi All,

We are facing below issue:

1) PO is created, approved and send to supplier.

2) We are using Isupplier.

3) Supplier requested change by changing the Promise date.

4) PO action history shows " Change requested" .

But Buyer has not received the Notification.

we tried below options:

1) Retry the workflow .

2) Rewind and retry the workflow.

Please suggest.

Thanks,

regards,

Yogesh