You can easily remove any Linksys WiFi extender errors by considering the steps below. 

Improve Device Software 

Go to the web management page of the Linksys device on a computer by filling in extender.linksys.com in the URL bar. After that look for the network advanced settings option and then click on the firmware update option. Now, if you see any latest software version file then download it on a computer. At last, restart the extender to do this method process. 

By Resetting Device All Settings

First, find the reset button which is mainly situated at the back of the Linksys WiFi device. Now, press that Linksys device reset button by inserting the hairpin in it. Next, all the LEDs of the Linksys device will now be turned off. Therefore, it means your Linksys device is completely reset now. After resetting all the settings you will need to do again the Linksys extender login and setup method process.