The provided system key is incorrect. Try each of the following until the issue is resolved:
1. Review your system key entry for accuracy. Make sure letters are upper-case. Double-check digits/letters that could be mistaken for the other, for example the letter O / the number zero or the letter S / the number five.
2. Check with your system administrator to review the system key in The Raiser's Edge.
3. Uninstall / reinstall app on mobile device.
4. If occurring for multiple users, generate a new system key.