The Cisco VPN Secure Client is a small app that runs on the user device to establish and monitor a VPN connection. It requires background services to be allowed to run at login/startup to function. Otherwise, the connection attempt will fail with a message like:

VPN connect capability is unavailable because the VPN service is unavailable

For example, on macOS under settings → Login Items, there may be about three Cisco items that need to be enabled. After enabling, reboot the computer and try the VPN connection again.