Attempting to upgrade to the newest SmartZone versions may result in an error saying "Upload image failed. Unsupported version."
This could happen if the current version of the controller is too old, so a 2-step upgrade may be required.
Refer to the target version's 'Upgrade Guide' document to corroborate the compatibility matrix.
Here is an example for the latest version 6.1.1
As depicted in the table, upgrade from versions 5.1.x or 5.2.0 and 5.2.1 is not supported, hence, in this case, the recommended path would be:
I hope this information is useful.
Refer to this KB for full upgrade process guidance.