I was in the same situation as you. The online tracker is different than your GC key. My agent has it on his account as well. But I recently asked him and he wasn't using the tracker as its less accurate than GC key. So as long as you can ask and confirm you can use the online tracker. You will need to create a new account different than your GC key account. When creating the account it will send a code to the email on file which probably will be of your agent, that was in my case. Get that code form him and you should be good. Following is the link:Hi, i have question regarding new tracker for checking application status, I applied through immigration lawyer, they have access to my file and gc key account. So am I able to make account on new tracker?
https://ircc-tracker-suivi.apps.cic.gc.ca/en/register