As the vehicle owner, you'll receive a PIN code from Volvo support to verify authorization for certain connected services. This does not apply to cars with Google built-in.
When changing ownership of a vehicle with connected services, there are some steps that need to be taken by both the previous and new owner.
If the previous owner of your car has not removed their profiles and connected phones, a factory reset of the car is needed. You can do this yourself via the car's center display or ask the previous owner to do it via the Volvo Cars/Volvo EX30 app.