There are several ways to get the LEDs to change - I'm not quite sure why the extension isn't working, however it's trivial to set up yourself. To change the screen on the sigma tile simply write any integer from 0 to 6 to the "Screen_Control" tag in Kepware - this can be done in several different ways.
1. The extension uses the IoT Gateway, which is well documented here: https://www.kepware.com/en-us/products/kepserverex/advanced-plug-ins/iot-gateway/documents/iot-gateway-manual.pdf - this is probably the most complex method due to updates to the ThingWorx platform.
2. The new best practice (and the method I recommend) is to add the screen control tag to your sigma tile asset using the ThingWorx Manufacturing apps. You can then write a service in ThingWorx to change the Screen Control tag based on what input you give it - if the service is directly on the Sigma Tile asset, it would simply be "me.<PropertyName> = x" where x is your input. You can then create a subscription to the alert (whatever you defined it as) to fire the service when that alert is activated.
Hopefully this helps,