Unfortunately, even if you were lucky to enter your username, either the loop continues or you likely receive error 403 page.
However, I had success in chrome (Kaspersky still on) with a combination of several methods and submitted my application yesterday.
Your goal is to get the username-password page (with methods 1-4 in combination with the 5th below). If you happen to get it and enter your username and password, you will most likely succeed further by just keeping applying the 5th.
1. as many suggest, delete cookies to break the loop (in my case only partly) and get to the welcome page with username and password.
2. enter a wrong username/password (or a wrong security question answer. It seems to help break the loop. Combine it with method 5.
3. try logging in in two pages simultaneously - in a regular chrome page and in an incognito page as suggested here by pantherstoner - https://www.reddit.com/r/ImmigrationCanada/comments/f09y87 Combine it with method 5 below.
4. alternatively, after you enter your correct username/pass, it may keep you in the loop. You may stay in the loop for 2-3 of rounds and see if it suddenly takes you straight to the next step (without even repeating username/pass) - the Agree page or even to the security question page. Sometimes it happens. Combine it with method 5 below.
5. Whenever you get 403 page - always use it- just to go back to the previous page whenever you receive the error and repeat your action on that previous page. If it doesn't work, repeat going back and forth 1-5 times, and you will finally get where you need.
You may either get the error403 page while logging in or later, e.g. during uploading your documents. Always try going back and forth in this case. Though with several attempts (back-forth), it always worked for me.
However, I had success in chrome (Kaspersky still on) with a combination of several methods and submitted my application yesterday.
Your goal is to get the username-password page (with methods 1-4 in combination with the 5th below). If you happen to get it and enter your username and password, you will most likely succeed further by just keeping applying the 5th.
1. as many suggest, delete cookies to break the loop (in my case only partly) and get to the welcome page with username and password.
2. enter a wrong username/password (or a wrong security question answer. It seems to help break the loop. Combine it with method 5.
3. try logging in in two pages simultaneously - in a regular chrome page and in an incognito page as suggested here by pantherstoner - https://www.reddit.com/r/ImmigrationCanada/comments/f09y87 Combine it with method 5 below.
4. alternatively, after you enter your correct username/pass, it may keep you in the loop. You may stay in the loop for 2-3 of rounds and see if it suddenly takes you straight to the next step (without even repeating username/pass) - the Agree page or even to the security question page. Sometimes it happens. Combine it with method 5 below.
5. Whenever you get 403 page - always use it- just to go back to the previous page whenever you receive the error and repeat your action on that previous page. If it doesn't work, repeat going back and forth 1-5 times, and you will finally get where you need.
You may either get the error403 page while logging in or later, e.g. during uploading your documents. Always try going back and forth in this case. Though with several attempts (back-forth), it always worked for me.