Thank you! I ended up calling the support every 30min until I wasn't disconnected and finally put on hold. The agent confirmed my oath form has been received by email and the next step is with the Mississauga office to make the e-certificate available.
The agent could not provide a reason why it's delayed (i.e. 15 business days vs the 2-5 timeline provided), saying it could either be a backlog at their office or a technical issue, and that I should be patient to receive it... Is there a way to contact the Mississauga office directly?