In any case, if you start getting a Wavlink extender not working error, you must check the error’s source first. As there can be many technical glitches that can cause this error in the extender. That can be due to the wrong placement of the extender, a weak connection, or your router having a technical error. Your internet plan might expire or stop temporarily. But, to solve that, you must reboot the extender first as this simple approach can help a lot. Just turn off the extender and leave it turned off for some time. After that, plug it in again using another power outlet and turn it on. 

If the error still persists, then check your networked device if that is compatible with the extender or not. Disconnect it from the network and make the connection again either through an ethernet wire or wirelessly. Later, open its web browser and clear the cookies, caches, and malware files. If your device has Anti Virus software installed, then check for its firewall and disable it if possible.