If you applied in March of 2015 and have not heard anything I would be concerned. What is the online service that you mentioned? There is no online service for family sponsorship applications.
I think it depends on the VO and if it's normal for them to acknowledge the receipt of additional documents. I emailed Mississauga (before AOR) letting them know I had made a mistake in my application and I sent a CSE later on to add my RPRF to my application and I received an acknowledgement email both times.