If you didn't receive a notification for a text message, confirm that you have texting enabled for the number, have the latest version of the iPhone app (4.1.6002 or above) or Android app (4.1.6100 or above) and have notifications enabled for the Grasshopper app. 

To do this Do this
Check to see if you have texting enabled
  1. Sign into your account on
  2. Go to Settings > Features > Grasshopper SMS and verify the texting feature is enabled. 
Verify push notifications are enabled
  1. On your phone, navigate to Settings > Notifications > Grasshopper.
Check settings within the Grasshopper app
  1. Go to Settings > Sync & Notification Setting in the Grasshopper app.
  2. Ensure that all boxes are checked off for the extension(s) that you want to be notified for on this device. 

For additional instructions on enabling notifications, please see the article Why are Push Notifications not working.