There can be multiple reasons for the setup errors. For example, if an interrupted power supply occurs, the extender might not get listed on the network list. A damaged and broken ethernet wire between the extender and the router can be another cause. Another cause is entering the wrong web or IP address to carry out the fixing up of the Linksys re7000 setup from the web portal https://linksys-wifi.com/linksys-re7000-setup/