I have encountered the same issue on two different PCs after upgrading to the RST 12.6 driver. The problem goes away after the storage driver is rolled back to RST 12.5.
It appears the 12.6 driver has changed the way storage devices are reported to the OS. I'm not sure if this was intentional or a bug, but I agree the Intel SSD Toolbox has fallen behind and a new revision is needed.