Once updated with the latest firmware version (Version 61, which should be automatically done a few hours after the installation) the device MUST sync its operation with all types of thermostats and HVAC systems.
If the device does not start when the main system starts working, there are only two reasons that can cause this problem:
1- The main system has a problem, so the air is not cold/ warm enough to activate the device's internal sensors, especially when the main system is in cooling mode; although the air coming from the vent feels cool, the main system is only circulating the air throughout the house instead of conditioning it. So the sensors do not feel any temperature difference when the main system is working or it is on standby.
To test and see if this is the case, you can follow these steps:
Make sure the main system has not been working for 20 minutes
Place a thermometer inside the vent and put the main system on fan-only mode (the main blower works without any heating or cooling activated), and read the temperature after 10 minutes
Now turn the heating or cooling on and wait another few minutes and read the temperature again.
There must be a drastic change (between 10 to 15 degrees F) between the two readings. If the change is less than 10F it means that the main system needs to be checked by a contractor.
2- The duct is disconnected from the main branch, and the flow coming from the vent is almost zero. Please note that the device is a booster fan. It will boost the flow that is already coming from the vent. So if the flow is zero, the device cannot be very effective.