Are you connected to any Corporate network / VPN connection ?
Can you please make sure you are able to ping and telnet the cluster ?
telnet cluster0-shard-00-00-jxeqq.mongodb.net 27017
In addition to this, Please confirm that port 27017 is not blocked by clicking http://portquiz.net:27017.
If any of this is an issue then I would suggest you to contact your IT department to see if there is a workaround or try to make the request from another location such as your home network.
Hope it helps!
Thanks,
Shubham Ranjan
Curriculum Support Engineer