Neither did I. I spoke to the customer service agent at IRCC yesterday and she said at times you don't get an acknowledgement. She suggested that I write an email to NDVO on
delhi-immigration@international.gc.ca with a screenshot/export of my email response asking them for an acknowledgement. That way atleast it'll be on our records that we replied. Use the same email ID that has been registered with your application.
Looks like we have the same COPR issue dates.. mine also got approved on 15th March 2020 but it expired in Aug. My 4-pt email also came in Sept and I haven't heard anything back from them since. Whenever I used to raise a webform or call them, I was told that my file is with NDVO and that I should wait. It's possible this email got auto-triggered as soon as we hit the 1 year mark of our COPR issue date.
Let's just hope we get our remedical requests soon. Best of luck!