If you have enabled SSO for your organization’s subscription but accidentally assigned the admin role to a nonexistent email address, or if you are unable to use SSO to sign in to your admin account for other reasons, please sign in using this link instead: www.grammarly.com/signin?ssoRedirect=false
It will allow you to sign in to your admin account without SSO. You can then assign the admin role to the correct account as described in this article: Transfer the admin role to a team member
If you also need to update your SSO configuration on the Authentication page without additional verification, sign in again using this link: www.grammarly.com/signin?ssoRedirect=false&secureLogin=true