Thanks. I tried but that also didn't workTry what the IRCC agent asked me to do. I know it's weird but give it a shot. Open the PDF that you received with instructions to download the e certificate.
In that PDF, there's a section for Downloading the certificate after all the paragraphs about creating account, invite code etc.
Click on the link to the portal in that download section paragraph, and then login to your portal account, the same way you've been logging in all along. It worked for me, I'm not sure if it means anything different but give it a shot.
(for a second, I thought that the URL in the PDF might have some additional parameters to "enable" the certificate or something, but it's the same URL that I've been using all along)
Do you remember if your tracker was updated to "closed" before you downloaded your certificate? Or is it updated now?