1) Check if the game is up to date (game version should appear in the bottom left).
2) If it is, and it’s still not working, you will have to manually whitelist this link http://151.236.217.77/version.php inside the router settings.
3) If whitelisting the link doesn't work, try to disable the antivirus and see if that fixes it. Usually Malwarebytes is the one causing this problem.