The charging cable is locked in the vehicle.
The Hypervolt Home device is not responsible for locking the cable inside your vehicle charge port. It is the electric vehicle which must release the charging port lock in order to allow the cable to be safely disconnected.
It could be that the vehicle did not end the charging session. You must end the charging session from the vehicle before removing the charging cable. Check the vehicle user guide in order to ascertain how this is done for your particular make and model.
Although each vehicle has different requirements for stopping the charging session, the charge port unlock button is usually found in the centre console, near the driver’s door or on the key fob.
If you are really stuck most vehicles have an emergency release cable you can pull, please consult the car manual to locate this.