What does the ERROR_CONNECTION_CLOSED message mean?
The ERROR_CONNECTION_CLOSED message indicates that the connection that your browser opened with a Zendesk page was closed without warning. Make sure your browser is correctly configured, as we explain in Zendesk Support system requirements, and you followed our recommendations for configuring your firewall for use with Zendesk.
To verify this is a security setting misconfigured in your network or computer, reproduce this issue from a different network than the one you are currently on.
A quick way to do that is by sharing the Internet connection from your smartphone to your computer. While testing, make sure to disable all other connections.
If you can't reproduce the issue using a different network, reach out to your local IT team to fix the problem affecting your local network.