The message [Could not switch the smartphone's Wi-Fi connection target to the camera.] is displayed.

The message indicates that the smartphone is connected to the access point, but that it was unable to switch the connection target from the internet to the camera.
When the camera is connected to the same Wi-Fi access point as the smartphone, it is possible to control the camera via the access point. Follow the instructions in "Connecting via an access point" to connect the camera to the same access point as Creators' App.