Error: 'OOPS! you are already signed in' when trying to verify an alternate email address

When you use a Yahoo email address as your alternate email to another Yahoo account and try to verify it, you'll see the 'OOPS!...' error. This happens because a browser can only hold 1 cookie and can't log into 2 Yahoo accounts at the same time. To fix the error, follow the steps below.

1. Return to the inbox where we issued the alternate email address verification link.
2. Highlight the verification link.
3. Right-click with your mouse and select Copy.
4. Sign Out of the Yahoo account.
5. In your Web browser's address bar, right-click with your mouse and select Paste.
6. Press Enter on your keyboard.
7. Sign in with your alternate email address and password.

Your alternate email address is now verified.