Sometimes after upgrading hardware to newer hardware appliances, installing or reimaging to a lower version that was previously running on the device does not work. This article provides information to explain this issue.
The newer hardware is compatible with the old firmware. When new hardware is released, the hardware configuration needs to be added to the firmware, and this firmware becomes the lowest version that this device can install, hence, installing or reimage to a lower firmware than that will not work.
Hardware releases are coupled with firmware releases. Make sure you check the Release Notes for the firmware that you are trying to install to verify if the device is compatible with the firmware in question. For example, if you are trying to install ExOS 7.4.7 on the Exinda 12064, it will not install because this device was released with version ExOS 7.4.9, so the lowest version it can install will be version ExOS 7.4.9.