Blocking Indicator not getting removed on milestone confirmation in PS

Dear Experts,

I have a issue in my project.

We have a scenario where Preq and PO getting created from PS activity.

We are using Invoice plan in this scenario. created in the Activity.

When we create Milestone and Invoice plan it will go for release process to get Preq released. after this PO will be created and GR will be done.

Problem: When PS confirms the Activity the blocking sign in PO invoicing plan is not getting removed.

Please explain me:

What configuration settings required to remove the blocking sign indicator in PO automatically.

Tell me Process steps if any.

Appreciate early response.

BR,

Arun