workflow for po release strategy

Hi guys,

We have configured workflow for PO release strategy. There are 4 levels of approval L1,L2,L3 and L4.

When PO is saved, mail is being received by L1. After L1 approving the PO, mail is not being sent to L2 onwards. When we check up "Activate event linking" in OOCU, the status is being updated to "deactivated" automatically.

What could be the problem?