Here in this model, you can see currently instance sits in Confirmation Screen user input task, but from user screen, this wasn't opened and process got closed showing "Action Completed" banner.
I've activity chaining all the way till this node. What could be the possible reason for it? Please advise.
Also, for this node, there are two instances at the same time, though the assignee is pp!initiator.
Discussion posts and replies are publicly visible
If the confirmation screen task is too many "hops" away from the previous user-attended interface (task, start form, or interface from which the process was launched), chaining will be broken and the behavior will show as you've described. The "number of hops" includes all chains between all nodes including subprocesses and loops. The standard environment chaining limit is 50 such "hops" - it's a little tricky to count them accurately, but in your case depending on what's in your 2 main synchronous subprocesses between the 2 tasks, it may or may not be being exceeded. Also every single chain in every synchronous subprcess would need to be chained for the chaining to be maintained - if even one is missing, chaining will break there.
Also I note that you have 2 incoming flows to your confirmation screen task (thanks to the AND node labelled "Split"), which is not really valid - chaining can only carry across one activity flow - you would need to have 1 of those flows just end and the other one can show the confirmation screen.
Thanks Mike, did the last suggested approach. It worked.