Question: What is the primary reason for sending Cause value = 12 (Location Area not allowed) to an MS?
Option 1: The MS has no subscription to operate in the current PLMN.
Option 2: The HPLMN determines that the MS, by subscription, is not allowed to operate in a specific location area.
Option 3: The MS's subscription has expired and it should find another cell in the same PLMN or an equivalent PLMN.
Option 4: The MS is not authorized for this CSG.
Explanation: Cause value = 12 (Location Area not allowed) is sent to the MS if it requests service, or if the network initiates a detach request, in a location area where the HPLMN determines that the MS, by subscription, is not allowed to operate. This cause is specific to the location area and does not trigger the MS to search for another allowed location area on the same PLMN.