I have three of those apps installed, none of them did anything that day. They've mostly worked in the past, except when larger areas were notified and you clicked on the notification to get more details the app would show nothing because whatever its service is running on was overwhelmed by the amount of people checking..

Meantime vacationing in Japan I can get a Japanese wall of text on my phone informing me and everyone around me who pulled out their phone of an imminent earthquake, all without data active.