After you have sent your home WiFi credentials through the app and the app sends it to the Ambi Climate device.
Your phone will then proceed to disconnect from Ambi WiFi and search for a connectable network from it's own WiFi list.
This error comes up if we detected that your phone cannot connect to any other network with connectivity. 

Make sure that your phone has your 2.4Ghz network credentials stored and that your network has connectivity (router is functioning properly with LAN cable securely attached and your current setup location has strong WiFi signal strength). If you get this error, navigate to your phone's WiFi settings and check that it has connected to a viable network.