The most likely culprit here would be an anti-virus or firewall program that's blocking OOTP from connecting to the PT servers. So the first thing to do would be to make sure OOTP is whitelisted in any of those programs that are running on your system.
If you're using a VPN, sometimes it can help to turn that off as well, though it's less likely that's the issue.
If you still can't connect after trying that, then please
submit a support ticket (or via email at
support@ootpdevelopments.com) so the support team can do some more advanced troubleshooting with you.