Please don't forget to do a full backup of the system before making the upgrade.
This should be done by default.
In problems you could just go back to the last functining setup.
Please read the Releases notes before upgrading and check if you need do more upgrading steps before you can upgrade from your version 9.21.x to the version 10.x in order avoid config miss issues.
After upgrading the controller to V10, you would be given a grace period of seven days to license the software with permanent activation key.
Apply the license key after upgrading the controller to V10. After the expiration of grace perios, the wireless controller would start generating event logs every 15 minutes, indicating permanent license key is required.
If you experience any issues with this process, please contact the GTAC for assistance.