I recently set my Autodesk account username to the following:
[object_Object]
After I made this change, I discovered that I was no longer able to login to my account on the Autodesk website. After entering my login details, I was just redirected to a blank page. This was tested on Firefox 86.0.1 and Edge 89.0.774.54.
I also tried pressing the "Autodesk Account" button in Fusion 360, where I was still logged in. This sent me to a blank page in my browser with the following error:
xoauth_problem=parameter_rejected&xoauth_parameters_absent=oauth_redirect_url&oauth_error_message=Invalid%20value%20for%20parameter%3Aoauth_redirect_url
The oauth_redirect_url parameter in the URL was the following:
oauth_redirect_url=https%3A%2F%2Faccounts.autodesk.com%2Fusers%2F[object_Object]%2Fview
After I removed the square brackets from my username, the issue stopped occurring.
I was asked by the live chat support agent to post this bug report here.