The firmware upgrade for 4RF devices works a little differently than most device types we use.

Instead of maintaining two slots for the active and inactive devices, it only keeps track of a titled record of the last firmware used.

So to "failover" to the inactive firmware version, you must first perform an Add Firmware Change to the device, and create a "temporary inactive slot" that will only exist until the next device restart.

At that point, you can perform the Restart Device to Inactive Image change request, and select the firmware you just pushed. This should restart the device to that selected version successfully.