If you came across an error message while connecting your gmail account, it is an indication that your browser has been blocking gmail from initiating a pop-up.
Follow these steps to disable pop-up blocker:
1. On the browser’s address bar (or omnibox in case of Google Chrome), a small icon on the right most corner known as the pop-up blocker icon will be present and it suggests that your pop-ups are being blocked by the Google Chrome browser.
2. Click on the pop-up blocker icon. You will be presented with a dialog box that shows that your browser is actively blocking all pop-ups by default. Select the option “Always allow pop-ups from” and click Done.
This will ensure that pop-ups from this URL will not be blocked in future.
Alternatively, you can click on the three dots to the further right of your browser > Settings > Privacy and security and enable popups from there:
3. Click on the gmail icon now. This will open a single sign-on (SSO) page that allows you to connect gmail to your web application's account successfully.