This can happen due to a poor network connection (e.g., ping time is too long) or firewall configurations. You can check the server's availability with Telnet and PowerShell on Windows and other tools on MacOS (Telnet, nmap, etc.).
This article explains how to use some of those tools to check for open IP/ports: How to check if Teramind IP addresses/hosts and ports are reachable.
Further connectivity tests and example output can be found in the How to diagnose network connectivity issues article.