I was just struggling with this as well. I figured out that they are looking for details from the initial SAML setup screens from the Google Admin Console. To see these from the GAC:
Once I did this, Google started authenticating users in Canvas.
Also, there are 2 logins for your Canvas environment.
- https://<Your Environment Name>.instructure.com/login/canvas - This is for manual logins. This works as a backdoor in the case your SSO is hosed.
- https://<Your Environment Name>.instructure.com - This is your SSO login.
I hope this helps.