Hi all,
the issue was resolved. In case anyone else experiences a similar problem, here are some steps that helped me:
1) check security groups on the cluster; if all traffic is allowed but you're still unable to connect, try adding an exception for SSH (port 22) anyway
2) check that you're not trying to connect from under VPN (and/or check outgoing firewall rules)
3) if public IPs aren't working, try public DNS names instead (if they're not showing, you might need enable them first)
4) don't rely on ping too much for diagnosing connectivity -- looks like you might be able to SSH without being able to ping
Best regards,
Nikolai