Topic
Issue Summary
The Nintex Robot was unable to connect to the server over HTTPS (port 443), displaying a message:

"Cannot access Nintex Servers. There might be a problem with your network connection or firewall settings."

 

Even though all services were up and running, the robot failed to establish a connection. Where as console and studio is working fine.

Root Cause
During troubleshooting, we found that:

• Port 443 (HTTPS) was open and listening via NGINX.

• However, IPv6 connections to port 443 were stuck in the SYN_SENT state.

• This was observed using the following command:

   

  netstat -aon | findstr ":443" 

   

Output
This indicated that the server was not completing the handshake for incoming IPv6 requests, resulting in timeouts or failed registration for the Nintex Robot.

Solution
We resolved the issue by disabling IPv6 system-wide, as the environment did not require it and the traffic was expected over IPv4.

Steps to Disable IPv6 via Registry

1. Open Registry Editor (regedit)

2. Navigate to:

    

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters
   
   

3. Create a new DWORD (32-bit) Value:

   • Name: DisabledComponents

   • Value: FF (Hexadecimal)

4. Reboot the machine to apply changes

Alternative via PowerShell (Run as Administrator):

powershellCopyEditNew-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters" `-Name "DisabledComponents" -PropertyType DWord -Value 0xFF -Force

Result
After disabling IPv6 and rebooting:

• The SYN_SENT state on IPv6 connections disappeared.

• The Nintex Robot was able to connect successfully to the server via port 443 (HTTPS).

• No further errors were observed on the robot login screen.

References

• Microsoft Docs: Disable IPv6 via Registry