Just wanna give an update on my situation in case in might be helpful to anyone.
To recap, we received Portal 1 email on Apr. 2nd from Etobicoke office, and we responded on Apr. 3rd. Then on Apt. 17th we received another Portal 1 email saying we had not responded, so we responded again immediately. Also my parents are in China and don't have any visas.
Today (Apr. 24th) I called IRCC around 9:20am Eastern time and go through after only a 15 minute wait. The agent told me that our response was uploaded to the system on Apr. 22nd and we just have to wait. From this it seems that our first email reply did not get through, or maybe the office was just late to update the system. Anyway in the afternoon we got PPR request email from Hong Kong office, so the wait is finally over.
Good luck to any family still waiting after 2 long years.