I think you're right in hindsight. Fixing this.

For anyone who comes across this later, this happened because we did an in-place upgrade. We simply moved the workflow from a clean 6.3 server and everything works now. We also, incidentally, had to modify our custom schema to include the Smart Tags field because our custom schema didn't include it....

We're on 6.3.1.2.

I don't even see that workflow. What did we do wrong? That's my question.

The documentation here - Smart Tags - indicates that it should be possible once Smart Tags are configured to start a workflow named "DAM Smart Tags Assets". I don't see that as an available workflow, though. What did I do wrong? I followed this documentation.  Configuring Smart Tags Cloud Service

arunp99088702​ - I just tried a sample of an EventListener and it worked. I was able to see which property changed. In their sample code ACS Commons warns against using this often, it seems, saying...This is why I've been trying to get the ResourceChangeListener to work. Plus it seems more precise. ...

So like I said in my own thread I opened​, I'm having trouble with the ResourceChangeListener. I haven't tried an EventListener yet. I'm worried that I'll go to the trouble of implementing it and land in the same place.

You're using the EventListener, it looks like. Like the user above I tried a ResourceListener like this. I tried this code from Stack Overflow as a sanity check. When I debug this the addedPropertyNames and changedPropertyNames properties of "change" are null. I would expect to see what changed here...

Sorry, I'm not sure if I'm misunderstanding, but the problem I'm seeing that's similar is I don't see the property changed / property added messages from Events. It appears to have been removed in AEM 6.3.              

I tried that and the data  what changed is null. So I can (through either the event handler or the resource changed listener) listen for resource changes. It just looks like the subsystem won’t tell me what actually changed, which is what I need to fix this service.