I think there are 2 topics here. There is a difference between being refused your application for permanent residency and not doing anything with your ITA.
The ITA is an invitation to apply, that means you have enough points to get an invitation to apply. In this case just like the answer below if you do not submit an application within 90 days then you go back to the pool. But be careful because your profile expires after one year.
If you get refused in your application for permanent residency (unless misrepresentation) you have to submit a new profile and start the process again (wait for an invitation, etc). You can create a new profile the very next day.