If you have received your AOR letter in the email, it has this link to check the status of the application -
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/check-status.html
It's a generic tool and it asks you questions about what you have applied for. Select relevant options from the dropdown and it will give you an option to register if you don't have an account.
Or you can directly go to
https://tracker-suivi.apps.cic.gc.ca/ to register for the tracker account. You will reach to this same link if you go through the generic tool mentioned above.
Fill in UCI and Application number, if it finds your application in the system - you will get a verification code in your email and you'll have to set a new password. That's it! You can now login using your UCI and password.
Till yesterday, I was getting this error while trying to register -
So it takes some time for ones application details to propagate to this system and then it lets you create an account. It took around 48+ hours for me after I received the AOR.