This means that the weather radio has not received the weekly test signals for over a week. Turn the radio off and then back on. Next set the radio to announce the current weather (on my unit the button is marked Weather) and listen to the broadcast. If you do not hear the broadcast, move the radio until you do.
If you can't get a good signal, check the NOAA site for your coverage area to see if the local emergency alert broadcast towers are under repair. If needed try one of the other towers that cover your county. Sometimes you may get one location better than the others if you are near the edge of the county or are surrounded by hills. http://www.weather.gov/nwr/Maps/
has the maps by state and those link to the frequency of each tower that can be heard in a given county.
If the radio still fails to hear the test alerts, you may need an external antenna or a new radio. (Caution: the external antenna may hear a more distant tower and not give your local alert. We got the wrong state on one radio.)
(who has one weather radio on each side of the house set to two different towers. I live 2 miles from the state line. We had severe weather a few days ago and only the in-state tower broadcast the severe weather watch. The local television stations displayed different watches and warnings depending on which NOAA coverage area they checked.)