Add on board

Ive been trying to locate information on how the add on board works... unboxing states no wired connection needed... Do both boards require a wifi connection? Or is there a magical connection that happens no one is mentioning? 

You need to put a wifi module in the add-on board.  Simply plug it into the power pigtail.   Use the same instructions that were used for the main board to add it to your wireless network. 

My Add -On Board was connected to wi-fi and initially recognized through SmartThings , but then i either accidentally removed it or connect was lost from Smartthings Smart App

The main board is still connected, configured and working but when I attempt to re-add the add on board  through Add a Konnected Device it is not found.

I have attempted to reboot the device, press and hold the RST button and the blue light  flashes a couple times but still nothing is being  recognized through SmartThings.  When I unplug and re-plugin the add in board, the blue light blinks a couple times and goes off, which the instructions also  indicate that it is connected to wifi.   What is the Flash button for on the add-on board, do I need to push this too?

How can I get SmartThings Konnected (Connect) Smart App to find the Add-in board when attempting to re-add it back in through Add a Konnected Device.