Solution
By default, a Value Change event that the Event Structure can recognize is only generated for direct user interactions with the Front Panel. In the case described in the Issue Details section above, the indicator value is changed programmatically, thus LabVIEW dose not generate a Value Change event.
Furthermore, Value Change events do also not occur when you use VI Server, global variables, local variables, etc. to change VI or Front Panel objects programmatically.
There is one exception: Events for changing Controls and Indicators can be generated programmatically with a Property Node, using the property
Value(Signaling) (in short:
Val(Sgnl)), like shown in the figure below.

It can e.g. be created by right-clicking the terminal of an Control or Indicator, then navigating to
Create » Property Node » Value (Signaling).

When data is written to the write-only property, the value of the referred Indicator/Control is updated, and an event is fired as if the Front Panel value was changed by user interaction. Be aware that the event is fired every time data is written, regardless if the value was overwritten by the same value. When e.g. using this property inside a loop, it will generate a Value Change event for each iteration, regardless of whether the value was actually changed.