I downloaded the Win64 version of taskcluster.exe from https://tools.taskcluster.net/index/artifacts/project.taskcluster.taskcluster-cli/latest and put it in my path. When I run |taskcluster signin|, I get redirected to an Okta login in a new browser tab as expected. After logging in, however, I get a Taskcluster page that only offers the 3 login options at the top and my credentials at the bottom - no "Grant Credentials" section in the middle.

I was able to successfully get a "Grant Credentials" URL from aki and change the port it was listening on and was then able to click the Grant Access button, which then allowed taskcluster to save the credentials.