Thanks for the interest in the plugin! I noticed the same thing today, it is missing. Again

If you can't wait, you can download it from here and install manually: https://download.dedroog.com/Plugwise_Pro_4.0.0.4.zip
Make sure to copy the HSPI_Plugwise_Pro.exe into the root of your HomeSeer directory, and unzip the images.zip to "html\images\Plugwise Pro"
Thanks!