It sounds like you need to perform a refresh of the data in your app.
The steps to perform this refresh are:
1. Open the SchoolMessenger app.
2. Go to the menu in the upper left corner.
3. Choose contacts.
4. Once in contacts, press the refresh button in the upper right hand corner.
5. This screen will still show an error, but when you open the menu from the upper left the second time, you will have access to Attendance. Messages will also be populated with all recent messages you were sent.
6. At this point, your app should be functioning normally again. If not, contact your building secretary to verify that the correct email address is in PowerSchool.