You're limited to signing into one account per browsing session with Single Sign-on.
You can sign into multiple accounts by starting additional browsing sessions with one of the following methods:
- Use browser profiles in Chrome or Firefox to switch between multiple accounts in separate windows.
- Open a private browsing session to sign into another account in a new browsing session.
- Use another browser like Firefox, Safari, or Edge to log into another account.
Single Sign-on authenticates one service (like Gmail) to one account. Each browsing session can only be logged into one SSO service at one time, so it's not possible to sign into different accounts in different tabs or windows.