Answer
Check whether the event's condition is comparing against the field's human-readable client-facing label, 'Out of Operation', rather than its actual underlying database/XML enumeration value — these commonly differ, with the stored value typically being the upper-cased label with spaces replaced by underscores, in this specific case 'OUT_OF_OPERATION'. Reference that underlying enumeration value in the event's trigger condition instead of the friendly display text shown in the client; checking the relevant Logical Unit's enumeration/domain declaration is the reliable way to find the exact stored value string to use in a given event condition, rather than assuming it matches the client-displayed label.