Q. Why do some organizational units (OUs) have a blue exclamation point next to them in Group Policy Management Console (GPMC)?

A. A blue exclamation point that's displayed next to an OU container in GPMC indicates that the container has Block Inheritance enabled, which means that settings made to parent containers aren't applied to the OU (unless the policy for the parent container has the "No Override" option configured).

You can confirm that Block Inheritance is configured for an OU that has a blue exclamation point by right-clicking the OU; "Block Inheritance" should be selected on the displayed context menu.

Learn more: Access Denied: Blocking Inheritance and Overrides in Group Policies