With this new batch of stuff, (and most of the previous batch too) there have been devices that refuse to be controlled via direct message by the PLM. After much reading this turns out to be caused by a "protocol enhancment" referred to as I2CS, or Insteon 2 with CheckSum. Part of the changes wrapped up with this is that the devices will not respond to direct commands unless the device is linked. How this relates to the direct command to go into linking mode I don't know.
Why Insteon chose to do this, I don't know. The reasons they give are
- Improved security of your devices
- Improved message integrity
However, I am not sure that these are valid. The security of your devices relies on linking the device to the PLM, but you can do that programatically, so it's simply one extra step before you can start meddling with the lights. The other reason while looks valid, this is what checksums do, fails to recognize that there is already a checksum in the insteon packet. A second checksum does not help this situation!