HomeKit cannot modify the state of a virtual presence sensor, they are treated as read only.
Some people use a virtual presence sensor that acts as a switch, because they want Hubitat Dashboard to show present/not present status. I don't use any dashboards in my home automation, so I just use virtual switches, and those switches do other things in Hubitat for arrival and departure.
If you want to have HomeKit change a virtual presence sensor in Hubitat, you need to use one that also has the switch capability. Then set your HomeKit automation to change the switch capability of the Virtual presence sensor and it will reflect present when ON and not present when OFF. @ogiewon 's Virtual Presence as Switch driver will do the trick.
If you don't want the Sensor and Presence Sensor capabilities to show in HomeKit, you can use this method.
