AiCam use iCloud for data exchange and authentication. The camera device and the viewer device must use the same iCloud account for this to work. The iCloud service may take some time to sync the data.
If you have a device which uses a different iCloud account, you can add it as a guest device. To add a guest device, tap on the button "Pair guest device" at the bottom of the Device screen. A guest device can view the camera live feed and receive push notification, but cannot view the event history.