Why does second sign in window appear?

@wdl0355

I'd recommend updating macOS when possible. Back to your question, it sounds as if there is a disconnect in what we call the shared lock state. Try the following.

1. Look for our helper in the menu bar near the WiFi indicator and the clock. Right-click (Option-click) on the helper and select Quit.
2. Quit your browser.
3. Open 1Password and unlock.
4. Open your browser.

That did the trick. Thanks for your helpful and prompt reply.

You're most welcome.