This means there is a fault on the panel, either something very benign ( like the system clock is not set or a low system battery ) all the way up to a major configuration or communications problem. You can press * + 2 to see the troubles on the panel. If it is the system clock, you can set it from there and be home free. It is probably a good idea to have the local alarm company come by and do an inspection and test, though, as the communications may be down ( last tenant ended the monitoring contract, phone line may be disconnected, etc.) and you probably want to change the user codes.