sudo /opt/cisco/vpn/bin/vpn_uninstall.sh
If that command is successful at removing the Cisco Secure Client, then start the installer again. If that command doesn't work because it can't find that uninstall program, then run this command in Terminal and try installing Cisco Secure Client again.
sudo pkgutil --forget com.cisco.pkg.secureclient.gui
If you have the older version of the Cisco AnyConnect client installed, run this command instead.
sudo pkgutil --forget com.cisco.pkg.anyconnect.vpn
If required, you can re-download the VPN client from our article titled Install the NC State VPN Client for macOS 11 and higher.