Update:Check the contact us section of the test invite PDF. It will have the email ID of your processing office.
Test Invite - Aug 13
Test given - Aug 15 and Aug 16
interesting, in test invitation which is came from "IRCC.DNPNTCITScheduling-PlanificationCITPTNRN.IRCC@cic.gc.ca" , inside PDF we have:
To contact us regarding your knowledge test and/or an accommodation request, please email:
(INSERT LOCAL OFFICE EMAIL ADDRESS)
It looks like IRCC forgot to add email there?