Since this was just a test only devices that were enrolled in the WEA test got the message.
Source: https://www.fema.gov/event/ipaws-national-test
“The WEA test will be directed only to consumer cell phones where the subscriber has opted-in to receive test messages, which will be in either English or Spanish, depending on the device’s language settings. Most mobile phones will not display the test message. In contrast, consumers will automatically receive real emergency alerts on compatible phones (even if they do not receive the test message).”
For instructions on how to enroll: https://www.fcc.gov/sites/default/files/weatest_opt-in_instructions.pdf
You would not get the WEA message unless you were connected to a cell tower:
Not Receiving an Alert
If someone near you received a WEA and you did not, it may be due to inadequate cell reception, or because when on a call, some mobile phones will not show an alert — this varies by make and model.
Not receiving an alert may also be because your mobile phone is:
*Set to “off” or “airplane mode” *Not connected to a cell site broadcasting the alert *Connected to a cell site that is not broadcasting the alert, undergoing *maintenance or is out-of-service *The device is opted out of receiving alerts. The location of the alerts opt-in/opt-out menu typically is in the notification settings menu. *If your mobile phone continues to receive the same WEA over and over it is most likely an issue with the device. Mobile phones should ignore subsequent re-broadcasts of a WEA but sometimes a device gets stuck in a loop repeatedly alerting for the same WEA. Powering off the device and turning it back on may help.
Source: https://www.fema.gov/emergency-managers/practitioners/integrated-public-alert-warning-system/public/wireless-emergency-alerts