question

@Jason Lightfoot 's suggesting is correct; you need to use the debug() command. This is because the Process Flow List activity makes a copy of its internal list for each instance of the flow. An instanced flow will make one copy for every instance. Even a general flow still has one instance, so the list is a copy.

If you are using a general flow or a global list in an instanced flow, you could consider using a Global List in the toolbox, and pointing your Process Flow list to the Global List.