Extenders LED lights are all green, but still no connection to the internet

From the sounds of it all this happened because you enabled smart connect. Smart connect needs to work with compatible devices because it dynamically switches devices from one band to the next. Neither extender is compatible with this.  You're mixing new/old technologies. 

If you want/need the extenders, you're going to need to turn smart connect off and utilize unique ssid's for the router and extenders. Otherwise you'll keep running into the issues you're having.