Sprint often disables access to all short codes (5- and 6-digit phone numbers) from their handsets. If you are a Sprint customer, and you receive a message such as "Message Failed. Shortcode may have expired or shortcode texting may be disabled," you may need to contact Sprint to enable your phone to send and receive messages from short codes. Nixle uses the 888777 short code to send you timely messages.
You may contact Sprint by dialing "*2" on your cell phone or visiting Sprint's website.