When a user logs in from your site, we will pop open a login window for your-org.tina.io. When log in is complete, we will attempt to send a message back to the main window.
The most common reason for this issue is when the callback URL is not ser properly for a Tina app. The main window's base URL will need to match the Tina app's "callback URL" exactly.
Make sure to include https in the Callback URL:
e.g:
Or if you are testing locally, it might be something like: