You must have an active network or Wi-Fi connection to receive an alert. If you do not have an active or strong enough connection when an alert is sent, the alert will be queued for a limited time and be sent to you once your device is connected.
Examples of offline situations include:
- No Network connection (Computer)
- the device being in airplane mode (cellphone)
- you have your cellular or Wi-Fi turned off
- you are out of range of a local cellular tower or Wi-Fi base station
- you are in a dead zone where the cellular or Wi-Fi signal is impeded