Uninstalling and re-installing the Check Point Endpoint Security client (version E75.01) worked for me too and I am using a static IP (not DHCP) on my mac mini. Note about uninstalling the Endpoint Security client E75.x and newer: Open the original DMG package you used to install the client and launch the Uninstaller shown.

Endpoint Security Suite and Remote Access Clients E80.51 Endpoint Security Client & Remote Access VPN Clients E80.51 Resolved Issues; To get a fix for an issue listed below contact Check Point Support with the issue ID. To see if an issue has been fixed, search for the issue ID in Support Center. For more information on Endpoint Security Clients E80.51, refer to sk101313 (Endpoint Security Clients macos - How can I make the Cisco VPN Client work with Lion I had serious issues with Cisco's client (it kept kernel panik-ing my Mac) and had the IT department help me set up the built in client. It basically works the same way as it does on an iPhone or iPad, so if you can connect with that device, you should be able to do so as well with your Mac. What I needed: the ip address of the VPN Server Cisco VPNClient – Error 51 – It's Me, Tommy

VPN client agent was unable to create the interprocess communication depot

Cisco Error 51: Unable to communicate with the VPN Configure the client by going to the System Preferences > Network > Click on the “+” sign below the list of interfaces, select VPN from the interface list and Cisco IPSec from the VPN type, click create and enter your settings and your good to go. A fix for 'Error 51' with the Cisco VPN Client - Mac OS X

Jun 17, 2019

Cisco VPN Client cannot connect - Error 51 Solutions